Integration with CKEditor

Current Status:
Basic Integration with CKEditor works. It supports all entity types and their corresponding view modes.

That being said, UI needs polishing and there's need for better error handling. If there's need for any feature, open a new issue and assign this issue as its parent.

Original Report:
I did a basic integration of the module with ckeditor. Right now all entity types, view modes etc. are not properly configured but it works for *node* entity type in *teaser* view mode.

Please provide some feedback on how this looks.

You need to add the 'E' button to ckeditor toolbar to enable this plugin.

I'll create sub-issues of this issue as required.