Minor cosmetic fixes

A couple of (mainly) cosmetic fixes. 

* Change the description of branding app in its setup.py
* Rename an image of Astakos UI to a more proper name
* Remove a deprecated section from quick install admin guide, urging the users to skip the network setup
* Provide a more verbose message on the Network tab of Cyclades UI, in case that no networks were found
* Return the proper message when trying to create a new IP and no networks exist