@djwfyi cursory review in case I missed something.
Closes#580
I do need to do further testing beyond the patches here. But I'm going
to handle that out-of-band.
This commit also generally cleans up the Installation docs and uses /includes/<platform>/steps-*.rst as a pattern for storing platform-specific tutorials within a single root URL.
Finally, due to API rate limits, this commit adds some Makefile magic to allow skipping of sync'ing dependencies. Pass `make BUILD_DEPENDENCIES=FALSE <platform>` to skip building any deps and use what is already in the branch.
