In #85 the voice context will be renamed to audio context, so the CValueObject classes will be renamed to namespace Audio too.
As #140 changes many CValueClasses, this crossover change is done in the same unit of work.
* prepared for login/off sounds
* prepared for text message sounds
* helper method to play sounds
* enabled mute / mixer also in cockpit, including context menus
* settings for notification sounds
* some minor tweaks, e.g. changed signal/slot to C++ style where missing
Some minor changes in the same step:
* Fixed some style sheets
* Added QToolBox as preparation for a status message list
* Renamed voice settings to audio settings
* rename CStatusMessages to CStatusMessageList
* rename NetworkVatlib to CNetworkVatlib
* replace all occurrences of Realname with RealName (correct camel case)
* CSequence method corresponding to CList::append is push_back
* don't compile the qdbuscpp2xml metadata plugin by default
* CAircraftIcao string members always trimmed and capitalized
* added CComSystem::roundTo25KHz
* using epsilon comparison in a couple of places
refs #81