[#61007096] fix mms agent install to not clobber /usr/local/share

also:
- mms_agent.install_dir now correctly points to the actual install dir, and not its parent
- added 3 new attributes to better control munin
- now creates the parent install dir if it does not exist
- use chef's file cache instead of tmp
- update download link with (new) canonical url, and changed 10gen to mongodb
- version bump

This was tested locally with Vagrant.

https://www.pivotaltracker.com/story/show/61007096 (this is the root cause for issues in that ticket)