#172 Unify cdk.renderer and jchempaint.renderer interfaces

[Nina Jeliazkova]

The JChemPaint and cdk-jchempaint currently provide similar rendering functionality , but is not possible to switch the libraries without modifying the code.

This proposal is to provide a common interface for the rendering /selection functionality , which will allow to have one e.g. IChemObjectSelection interface instead of the two currently available :
org.openscience.cdk.renderer.selection.IChemObjectSelection
org.openscience.jchempaint.renderer.selection.IChemObjectSelection

This will allow interchanging jchempaint and cdk-jchempaint by loading the related implementation classes, without the need to replace within the user code one interface with another.