added more documentation on qt signals and the qt event queue which is

a common source for problems when plugins are developed

added example code that injects new signal after emitting addEmptyObject, to ensure new object was processed by all plugins.

closes https://www.graphics.rwth-aachen.de:9000/OpenFlipper-Free/OpenFlipper-Free/issues/110

added 1 commit

• 4d5e0a73 - revised documentation for addEmpty object

Compare with previous version

mentioned in commit 4dbf9d16

merged