Update code per eslint

[ianb]

It's hard to tell because of other test failures, but npm run lint:js now fails due to some new eslint rules and other updates that have come in since then:

/Users/ianbicking/src/pageshot/addon/bootstrap.js
   32:15  error  'Services' is not defined               no-undef
   55:5   error  'Services' is not defined               no-undef
   59:5   error  'Services' is not defined               no-undef
   82:5   error  'CustomizableUI' is not defined         no-undef
   83:23  error  'CustomizableUI' is not defined         no-undef
   92:23  error  'CustomizableUI' is not defined         no-undef
   98:5   error  'CustomizableUI' is not defined         no-undef
  142:24  error  'LegacyExtensionsUtils' is not defined  no-undef
  168:24  error  'LegacyExtensionsUtils' is not defined  no-undef
  216:19  error  'AppConstants' is not defined           no-undef
  228:7   error  'Services' is not defined               no-undef
  247:22  error  'PageActions' is not defined            no-undef
  247:53  error  'PageActions' is not defined            no-undef
  247:79  error  'PageActions' is not defined            no-undef

/Users/ianbicking/src/pageshot/addon/webextension/background/analytics.js
  162:11  error  Strings must use doublequote  quotes
  163:22  error  Strings must use doublequote  quotes
  163:43  error  Strings must use doublequote  quotes
  164:20  error  Strings must use doublequote  quotes
  164:39  error  Strings must use doublequote  quotes
  166:17  error  Strings must use doublequote  quotes
  167:17  error  Strings must use doublequote  quotes
  167:36  error  Strings must use doublequote  quotes
  170:11  error  Strings must use doublequote  quotes
  171:22  error  Strings must use doublequote  quotes
  171:43  error  Strings must use doublequote  quotes
  172:20  error  Strings must use doublequote  quotes
  172:39  error  Strings must use doublequote  quotes
  174:17  error  Strings must use doublequote  quotes
  175:17  error  Strings must use doublequote  quotes
  175:36  error  Strings must use doublequote  quotes
  178:11  error  Strings must use doublequote  quotes
  179:22  error  Strings must use doublequote  quotes
  180:20  error  Strings must use doublequote  quotes
  180:39  error  Strings must use doublequote  quotes
  182:17  error  Strings must use doublequote  quotes
  183:17  error  Strings must use doublequote  quotes
  183:36  error  Strings must use doublequote  quotes
  186:11  error  Strings must use doublequote  quotes
  187:22  error  Strings must use doublequote  quotes
  188:20  error  Strings must use doublequote  quotes
  188:39  error  Strings must use doublequote  quotes
  190:17  error  Strings must use doublequote  quotes
  191:17  error  Strings must use doublequote  quotes
  191:36  error  Strings must use doublequote  quotes
  194:11  error  Strings must use doublequote  quotes
  195:22  error  Strings must use doublequote  quotes
  196:20  error  Strings must use doublequote  quotes
  196:39  error  Strings must use doublequote  quotes
  198:17  error  Strings must use doublequote  quotes
  199:17  error  Strings must use doublequote  quotes
  199:36  error  Strings must use doublequote  quotes

/Users/ianbicking/src/pageshot/server/src/pages/shot/controller.js
  18:7  error  'hasSeen' is never reassigned. Use 'const' instead  prefer-const

/Users/ianbicking/src/pageshot/server/src/pages/shot/editor.js
  169:15  error  Expected '===' and instead saw '=='                     eqeqeq
  169:48  error  Expected '===' and instead saw '=='                     eqeqeq
  192:28  error  Strings must use doublequote                            quotes
  208:23  error  Strings must use doublequote                            quotes
  220:26  error  Strings must use doublequote                            quotes
  529:32  error  Expected '===' and instead saw '=='                     eqeqeq
  543:25  error  Expected '===' and instead saw '=='                     eqeqeq
  563:3   error  Expected to return a value at the end of method 'draw'  consistent-return
  568:25  error  Expected '===' and instead saw '=='                     eqeqeq
  568:28  error  Strings must use doublequote                            quotes
  587:32  error  Strings must use doublequote                            quotes
  592:11  error  'rect' is never reassigned. Use 'const' instead         prefer-const
  600:9   error  'rect' is never reassigned. Use 'const' instead         prefer-const
  607:10  error  Unexpected var, use let or const instead                no-var
  608:11  error  'endX' is never reassigned. Use 'const' instead         prefer-const
  609:11  error  'endY' is never reassigned. Use 'const' instead         prefer-const

/Users/ianbicking/src/pageshot/server/src/pages/shot/view.js
  350:9   error  'highlight' is never reassigned. Use 'const' instead  prefer-const
  350:32  error  'highlightEditButton' is missing in props validation  react/prop-types