configuration properties package with tests

[dpolivaev]

Added package saves all chart configuration properties which can be edited by swing editors so that they can be serialized in any format as a key-value property map.

I am going to use it with https://github.com/freeplane/freeplane so that configured charts can be saved in freeplane mind maps.

[dpolivaev]

Including this logic in the editors could be better from the locality perspective if the editable properties are changed. On the other side, this package is already pretty complicated and the new code seems to be easy enough.