Allow workboard background colors to be configured
Summary:
Adds a UI for selecting background colors.
You can choose "Use Parent", which is the default, and allows you to set a color that all descendants inherit.
You can also choose "None", if a parent has a WHACKY BACKGROUND that you refuse to put up with.
Test Plan:
{F1114588}
{F1114589}
Reviewers: chad
Reviewed By: chad
Differential Revision: https://secure.phabricator.com/D15279