Spam Detection, Assest library fixes and settings styling improvements

Spam Detection:
* merged despamilator spam detection library
* introduced new settings for spam
* modified spam library for new spam settings

Comments Listing:
* Pending, Approved, Rejected, Spam list
* Action menu
* Block author
* Detect spam in all pending comments

Article Listing ordering changed to created_at desc

Asset Selector
* Style fixes, Now includes 5 assets in a row and some padding around wrapper
* Collections accordion fixed
* Searching fixed

Settings
* Styling improvements
* now shows help for each setting
* hide control column if there is no control

Dashboard
* Discussion statics are now linked to their pages
* Only non-spam pending comments will appear on dashboard

installer
* In installer generator I have added rake gluttonberg_engine:install:migrations. This will copy engine migrations in host app.