Update EventChord to include a ChordSemantics event entry which captures input semantic information…

Update EventChord to include a ChordSemantics event entry which captures input semantic information from chord mode and uses it to create chord names.

Without these semantics, naming chords based only on their notes results in ambiguous naming:
Example: Cm7 no root and Eb both have the exact same notes, and so there is no way to differentiate between them, unless we capture the data from chord mode: { cm:7.1 } as opposed to { eb }

[pkx166h, 2017-11-02 16:37:29]

Charles I posted a comment on the LilyPond Tracker issue that was created for
this.

https://sourceforge.net/p/testlilyissues/issues/5224/

I'll past it here:

I don't understand the reason for the dozens of files that are changed in your
patch. Why you also have added a 'README.md' file (we don't tend to do that),
the documentation files that have changed seem to contain diffs that have
nothing at all to do with the description of your patch at all.

I wonder if you have made a mistake here and not rebased your changes against
current master or are basing it off some other branch?

I cannot test the patch as it is at the moment. Sorry.