Added the following features to the stacks views:
- Add block from clipboard
- Rename the stack
- Duplicate the stack
- Reorder stacks

The renaming also supports workflow. For the duplication, workflow was not implemented as the original "add" functionality does not support workflows either.
Removed unnecessary if clause.
Changed a couple of long tags into short tags.
Merge branch 'improved_stacks' of https://github.com/ahukkanen/concrete5 into ahukkanen-improved_stacks
minor tweaks