#193 More general stereochemistry framework

[Egon Willighagen]

This patch generalizes the stereochemistry framework which is now focusing on IAtomParity.

• introducing IStereoElement, a super class indicating some form of molecular stereo chemistry
• IAtomParity extends IStereoElement
• IAtomContainer no longer has get/set of IAtomParity
• IAtomContainer now takes a list of IStereoElement's
• Added the helper method AtomContainerManipulator.getAtomParity(IAtomContainer, IAtom) to
  ease transition

The idea is that later patches (on which I am working) will introduce subinterfaces, like:

ILigancyFourChirality: CLOCK_WISE, ANTI_CLOCK_WISE (used by e.g. SMILES),
ICisTransIsomerism: E, Z,
IAxialChirality, and
IHelicalChirality.

[Egon Willighagen]

[Rajarshi Guha]

Looks good. Applied to master and pushed

[Rajarshi Guha]

Looks good. Applied to master and pushed