[PATCH] Add a color setting for MapCSS

[taylor.smock]

Subpart of #10435.

Possibly significant modifications for plugins:

• NamedColorProperty extends AbstractToStringProperty<Color>. I'm waiting for a find to get all the instances of NamedColorProperty in plugins, but it is taking awhile (find . -name '*.java' -exec grep -li "NamedColorProperty" \;). I don't know if this will require a recompile of any plugins.

Notes:

• Overrode storeDefaultValue to avoid an NPE. This is required since required final variables are not yet set (a different fix would be to make them non-final).
• Color boxes are not in the same column as the check marks (I'm not certain this is possible without a lot of work, or even desirable -- there might be a case for a colorboolean setting in the future, for example).

[taylor.smock]

Initial colors setting for mapcss