#74 Colour coded area views

[David Ross]

I've written a couple of patches for showing week and
month overviews by usage. It uses green for lots of
availability and red for less availability, this can be
controlled via the stylesheet though.

I've seen a few other requests for something similar to
this but not quite anything with this implementation, I
hope someone else can make use of it or perhaps
incorporate it into the main codebase as an option.

[David Ross]

Area overview patch against mrbs 1.2.2

[David Ross]

Month overview screenshot

[David Ross]

Week overview screenshot