Fix JSHint errors. Enable strict mode.

[panuhorsmalahti]

Fix most JSHint errors in lib/cradle/database/attachments.js and lib/cradle/database/changes.js. Added a FIXME comment about use of non-declared 'cached' parameter.

[indexzero]

What .jshintrc are you using? If we're going to make lint changes please use my styleguide: https://github.com/indexzero/styleguide.

[panuhorsmalahti]

I used the default settings of JSHint, which is the "golden standard" of linting. I'll have to take a look later on how the styleguide you linked differs from the default rules. If the .jshintrc differs from the default settings I think the file should be added to cradle's repository.

[indexzero]

@panuhorsmalahti the styleguide itself is the lint files. It's so I don't have to maintain 100 different lint files in 100 different projects. See how I used it in http-server: http-party/http-server@9fbfae5#diff-1

[indexzero]

That is just add the following to the package.json:

{
  // other values
  "scripts": {
    "pretest": "stylezero lib/ test/"
  },
  // more others values
  "devDependencies": {
    "stylezero": "2.1.1"
  }
}