Disable pasting action for mails

![bildschirmfoto 2014-11-12 um 10 30 17](https://cloud.githubusercontent.com/assets/485755/5007896/05be79c0-6a57-11e4-88c6-0ca08cbac8f5.png)

Additionally I've cleaned up the tests and fixed the available expression in the paste action.

@deiferni please have a look ...

Nope, I've adjusted the `actions.xml` and rebased it.