fix checkbox width
fix menu icons for WP3.8
Migration for ContributorGroup Table
Autofill for Group and role slugs
Further advantages for the convert_to_slug function
Again advantages to the convert_to_slug function - I think we are done now ;)
Added Description for Roles and Groups
Added Contributor name to edit screen
Add Preview for the avatar field
Enhancements to Avatar preview
Fixed Bug with empty contributor object
Fixed bug with the avatar field
Further advantages in UI
Further Advantages for the Contributors Table
Added Job title for Contributors
replace old menu icons with SVG icons
Many Changes (see description)

* Icons for Contributors Table
* Moved Flattr into own column
* CSS adjustenments
* Code polishing
Code polishing
contributor list table: configurable columns in screen options
Merge branch 'fix-screen-options' into contribrefine2