Option to ding on each new IM for given private IM sessions

Ding noises configurable via LiruNewMessageSound* debug settings
Move RP Mode check into the Profile button dropdown
Add buttons back to the IM floater, taking the space that RP Mode once occupied

Also fix concise IM buttons from looking awful, concise stays concise, only the dropdown button there.
Includes cleanup in llimpanel.* and llimview.cpp
Improvements to NewIMsPerConversation mechaics and includes cleanup in lloverlaybar.cpp
At the Singularity group's request: Another attempt to mute voice upon reconnecting to local voice if the setting requests such