Don't attempt to constrain values in setters
Make ol.control.Control extends ol.Object
Basic support for text symbolizers

This adds basic label rendering for points and polygons to the
canvas renderer, and a text symbolizer to the style package.
Fixing merge errors from unmerging #404
Use 'text' instead of 'name' for the label text
Changing renderLabels_ method name to renderText_
Prevent buttons from setting out-of-range brightness/contrast/saturation values
Stop buttons from moving so much when changing values
The map now has a collection of controls
Add 'units' property to ol.control.ScaleLine
Add addControl and removeControl methods to ol.Map
Proper handling of defaults
Adding TODOs
Updating example to use new properties
Merge pull request #770 from ahocevar/text-symbolizer

Basic support for text symbolizers. r=@bartvde,@tschaub
Do not call setMap(null) if control not in map
Add 'projection' and 'coordinateFormat' to ol.control.MousePosition
Meaningful variable names
Merge pull request #798 from twpayne/fix-layer-setters

Don't attempt to constrain values in setters
Merge pull request #800 from fredj/control_object

Make ol.control.Control extends ol.Object