Shorten URL by default in Permalink widget

And make «send by mail» usable.

Before: guess which button actually send mail ? :sweat: 
![capture decran 2014-05-23 a 12 08 57](https://cloud.githubusercontent.com/assets/21686/3065436/6a85188c-e262-11e3-8db7-f097165ae8d6.png)

After:
![capture decran 2014-05-23 a 12 05 26](https://cloud.githubusercontent.com/assets/21686/3065437/6f7aff00-e262-11e3-88d3-475444a03de7.png)

See https://github.com/camptocamp/c2cgeoportal/pull/961