bugfix delete features #18
comments added
variance propagation for conversion from polar to cartesian coordinates #22
added exchange object for creating feature and changed create functions (now 1 function for alle feature types). #25
added exchange object for nominal data and comments.
fixes #26: after editing the group name in the filtered table view you can now select another feature
start implementation of plugin manager #8
Merge branch 'master' into task_benedikt

Conflicts:
	controller/controller.cpp
	openIndy.pro
bugfix delete feature (index out of range after a feature was deleted)