Run doxygen on full include dir and provide full C documentation in RTD

[JoelPasvolsky]

Currently RTD generates and displays very partial C documentation:

This update runs doxygen on all files under /include and displays namespaces, classes, files, and structs:

[JoelPasvolsky]

Another option that is more elegant as long as we always want to build C docs for all include files is:

INPUT                  = ../include
...
RECURSIVE              = YES

[JoelPasvolsky]

@boothby, if we want to go with this more or less, I've got it working now locally for the SDK too.

[boothby]

The recursive option certainly seems easier to maintain.

[JoelPasvolsky]

I changed to the recursive method. Doxyfile has an EXCLUDE option that can then be used if we do want to exclude some subdirs in the future.

[JoelPasvolsky]

The AppVeyor failure is not related to this PR:

File "C:\Python35\lib\site-packages\dwave\embedding\chimera.py", line 109, in find_clique_embedding
    raise ValueError("cannot find a K{} embedding for given Chimera lattice".format(len(nodes)))
ValueError: cannot find a K13 embedding for given Chimera lattice

[boothby]

yeah... ironic when you test against an older implementation as a reference and discover a bug in it... this is very low on my todo list right now but it's safe to ignore

[arcondello]

Is this ready to merge? @JoelPasvolsky @boothby