Patch with various improvements

[Gary Oberbrunner]

This patch does the following:

• rename cummulative -> cumulative everywhere (spelling fix)
• remove periods from milestone names when making graphs; otherwise matplotlib gives error.
• Change DayLocator ticks to 7 day intervals in one chart where the dates were too bunched together. Could be configurable?
• setenv HOME to /tmp for matplotlib in two places
• workaround removing nonexistent value from list in model.py

[garyo@…]

various fixes & minor improvements

[Bhuricha Deen Sethanandha]

Thaks for the patch!