feature/491: listing page for walkthroughs

* created a teaser view for walkthroughs
  * with edit link, if user has the permission
* themed the small widget for make it usable
fetaure/491: fixing problems reported by reviewer.

* use the l() function
* use the format_date() function
* check permission in preprocess.
feature/491: fixing problems reported by reviewer.
feature/491: fixing reported errors.
Merge pull request #73 from csanyiarpad/feature/491-walkthrough-listing-page-theming

feature/491: listing page for walkthroughs
Improves screening.

* better error handling
* variables named properly
* generates dummy screening node on walkthrough creation
Merge pull request #74 from tamasd/master

Improves screening.
Update Drupal core to 7.28
Hide the contents of CHANGELOG.txt
Add chosen module and library

https://drupal.org/project/chosen
Enable chosen module on site install and site update
Theme selectbox to match Walkhub style
Merge branch 'master' into feature/collections
Merge pull request #75 from hosszukalman/feature/collections

Enable og access module ad rebuild node permissions
E_NOTICE fixes.
Merge branch 'master' of github.com:Pronovix/WalkHub
Removes unnecessary cases.
Merge pull request #76 from tamasd/master

E_NOTICE fixes.
Merge pull request #77 from Coornail/update/core-7.28

Update Drupal core to 7.28
Merge pull request #78 from Coornail/fix/158-confusing-collection-selection-widget

Fix confusing collection selection widget