WIP (read questions please): Don't display more than one flash message of the same type

Pull request for issue #231. 

### *Changing more then 3 items*
![kotti_multiple_delete](https://f.cloud.github.com/assets/1387542/1041566/954a737a-0fd4-11e3-8faa-25402a4faf23.png)

### *Changing less then 3 items*
![kotti_less_then3_copy](https://f.cloud.github.com/assets/1387542/1041585/363f1f06-0fd5-11e3-8249-614145afc2e1.png)

### *Pasting more then 3 items (with errors)*
![kotti_multiple_paste_errors](https://f.cloud.github.com/assets/1387542/1041590/7569e7ce-0fd5-11e3-88f8-937c4e77f69c.png)

### Overview
If we delete/cut/copy more then 3 items, merge the messages into one "n items were deleted/cut/copied/pasted". 

If we change 3 or less items, we still get 3 different info messages, each with a title. Do we leave it like this, do I merge them into one message saying something like "Items Name1, Name2 and Name3 were deleted/cut/copied/pasted", or do we go with the proposal in the original issue report change the "limit" from more then 3 items to 2 items or more?

Still a WIP until the question above is answered, tests are added and we get at least some translations.