Enhancement: Makes URL TVs fit into the UI

Fixes issue: https://github.com/modxcms/revolution/issues/3639

before:
![bildschirmfoto 2014-06-24 um 15 51 08](https://cloud.githubusercontent.com/assets/445501/3372713/3a21b31c-fbad-11e3-9f54-09b0374eca09.png)

after:
![bildschirmfoto 2014-06-24 um 16 34 56](https://cloud.githubusercontent.com/assets/445501/3372716/3d59de2e-fbad-11e3-85cb-e81883465629.png)