Change RAILS.root to Rails.root
Speed up renderring of keywords. for issue #189
Speedup category#show page: Show sheetcells distribution instead of showing all of them
Better display of categories in datagroup show page. for issue #194, #195, #198
Disable search for category for now. related to issues #132 #161
stopping deleting sheetcells while deleting datacolumns. for issue #191
Provide a way to protect datagroups from being cleaned up by crontab task. related to issue #191