Allow coloring specific dates a custom color.

[dsmeltz]

We run sprints where I work and it would be useful to be able to denote sprint start and end days along with code cut-off days. Colors should be visible in the mini calendar.

Some ideas:

• Have a tag, which you could associate a with a color, then tag the day. Sort of a named color thing. Not sure how to facilitate the tagging a day bit
• Simple right-click context menu item where you could set the color.

[hamnerben]

This