Re-use eigenvalue/-vector storage arrays in RawEigenvalue.doDecomposeGeneral when applicable

[hanslovsky]

Currently, Vt, e, and d are created as new instances for every call to RawEigenvalue.doComposeGeneral:
https://github.com/optimatika/ojAlgo/blob/master/src/org/ojalgo/matrix/decomposition/RawEigenvalue.java#L1060-L1062
Creating new instances could be avoided by re-using these objects when applicable, i.e. matrix dimensions do not change.
As far as I can tell that would require an additional member variable to store the double[][] that is referenced by Vt in doDecomposeGeneral.

[apete]

Done + a couple of other minor improvements. Please verify everything still works.

[hanslovsky]

Just pulled the current master and confirmed that I still get the correct result. Thank you for your swift reaction to this request.

[apete]

It will be some weeks before a new ojAlgo release - second half of April is my best guess.

[hanslovsky]

There is no need for rush here, imglib/imglib2-algorithm#29 is not urgent, so I do not mind waiting for that release.