Tabs

Added a tab functionality to the logging area.

Default tab is a channel tab, which handles channel and server messages.
A seperated tab is created for every user.
If a tab is updated or the assigned user leaves the server, this is indicated by a different tab color.
All tabs are movable and user tabs are closable with a rightclick.

Also removed every use of qteLog, to generalize operations on the log properties.
![mumble_tabs](https://f.cloud.github.com/assets/5446468/1325207/84c4c66c-34c4-11e3-8a0e-46a4e19bc147.png)