Refactors the clipboard_select_tag helper.

Same behavior, just cleaner code.
Do NOT rescue exceptions in test environment.

Except these are CanCan::AccessDenied exceptions.
Merge pull request #426 from robinboening/robinboening/clipboard_select_tag

Refactors the clipboard_select_tag helper.
Merge pull request #428 from robinboening/master

Adds a Tasks::Helpers module to encapsulate logic from rake and capistrano tasks.
Removes pending spec
Converts the Picture#edit_multiple form into non table layout.

Also:

- Fixes a bug with the autocomplete tag list field.
- Achieves 100% test coverage for Picture model.
Removes assignment of unnecessary local variable in autocomplete tag list field partial calls.
Updates the README master branch note. [ci skip]
Removes accidentally included DummyApp tables from 2.6 migration file. Closes #431

Also removes the forcing of table creation.
Changes the way we check for existence of alchemy tables in migration.

We rejected the whole migration if only the alchemy_pages table exists. Now we check for every table first if it exists and then create it. This way the migration could be run a second time, if someone accidentally removed one of the tables.
Removes the shorten_to option from essence_richtext_view.
Validates for uniqueness of Content name in scope of element.