CDB_CartodbfyTable function. Closes #169.

Have rails install a _CDB_UserQuotaInBytes() function to advertise
user setting so that quota triggers can call into that function
to know what is or isn't allowed. To install in existing db, run:

 rake cartodb:db:reset_trigger_check_quota

Tweak some rake tasks related to creating table triggers to basically
end up calling the cartodbfier function