Moved and renamed menu entries to improve the usability, global css, icons for social networks

- The menu entry for defining the delegations is moved to the settings (it is a setting, so it is expected there)
- There is now a global.css. There was the problem in the past, that new stuff like the embedded link information had to be added to every theme. In the global.css can be now be used as a basis.
- Social network icons are added (they are used in the corresponding addon settings)
- The menu entries in the settings are renamed. The word "settings" is removed from the entries, since this is some kind of tautology. The "connector" entry is renamed to "social networks" since this is more obvious.