Support colors for select from map markers

[lognaturel]

• Given that I have a form definition with a select from map
  And that a select option has a value set for a property with name marker-color
  And that the value is valid based on the criteria below
  When I open the select from map question
  Then the marker for that option should be the specified color

• Given that I have a form definition with a select from map
  And that a select option has no value set for a property with name marker-color
  When I open the select from map question
  Then the marker for that option should be the default color

• Given that I have a form definition with a select from map
  And that a select option has a value set for a property with name marker-color
  And that the value is NOT valid based on the criteria below
  When I open the select from map question
  Then the marker for that option should be the default color

Color criteria from simple style spec:

// Colors can be in short form:
//   "#ace"
// or long form
//   "#aaccee"
// with or without the # prefix.
// Colors are interpreted the same as in CSS,
// in #RRGGBB and #RGB order.

Select options may come from a geojson file, a csv file, or be internal to the form.