CW-512 druplicate nodes in cart

I fixed the following bugs:

1. Translation > Sources: As it was said during the functional meetings, you have to remove the following fields from the filter: Nace Code, Thesaurus and Author
2.  Sources: To facilitate the filter of the content by Activity and by Workflow status it should appear a dropdown in each field
3. Translation > Cart: The button to remove all the languages selected is missing - Radu made it Checkbox, I changed to BUTTONS
4. Now, the user can select twice the same content to add it to the cart - Note: The content now dissapears when is already added into the cart. The button "Add to cart" from the Node page - becomes disabled.
5. Hidden the links not present in the mockups
6. Added field with page_count / character_count for each node - which are populated during save + drush command to calculate statistics for existing nodes. These two fields are present in node selection view ...
7. Removed workflow_status field from all the content types.