Improved the stacks view

Added the following features to the stacks views:
- Add block from clipboard
- Rename the stack
- Duplicate the stack
- Reorder stacks

The renaming also supports workflows. For the duplication, workflow was not implemented as the original "add" functionality does not support workflows either.

![stack-improvements](https://f.cloud.github.com/assets/864340/2368654/f7c527f6-a7b5-11e3-9b67-dd84f25e6723.png)