Fixes db issues, no upgrade scripts yet

This fixes the issues with MM.db by asserting that some tables will be 'global', and some tables will be 'site specific'.
This pull request does not allow for a table to be both 'global' and 'site specific', although the change could be made to merge a site specific result set into a global result set within MM.db.get
There is no upgrade path with this pull request, all current database data will be lost, with files from the content plugin also being orphaned.