Added groupchat topics to uTox.

And other small fixes.

use /topic in a group chat to change the topic.
Fixed possible issue.
Added colors to group chat name list.

People sending audio to the chat have red names, we have a green one.
Group names are now drawn on two lines instead of only one.

It's a bit ugly but you see more names than before.
Added button to send audio to audio group chats.

By default, audio is not sent.
Fixed text bug.
Fixed audio bug.
Fixed group audio bug when switching output devices.