new skin for DrumComputer

modified RtMidiWrapper.
Listen for events among all devices
better cleanup using std::unique_ptr

new dialog to capture midi events for binding a
device to RackElement parameter (e.g. synth, mixer, ..)

some interface changes (added missing consts)

added some missing includes

fixed control issue.
all controls should now only react to the left mouse button

helper class for dynamic context-menus

fixed blocking on exit due to non-terminating background thread
fixed wrong deletion order within context causing a crash

fixed another cleanup issue on exit

improved the whole timeline.
	smaller memory footprint
	improved redraws
	better caching
	much faster

improved project-file for better module selection

fixed some compiler warnings when compiling without some modules

removed some deprecated methods

added exception handling for generator-thread
	e.g. broken pipe to soundcard or a failed initialization

new interface for exports as they need additional methods
compared to normal SoundSinks