Include files for quickstarts had a page title that resulted in a
duplicate H1. This removes the duplicate and moves the links for video
to the index.rst page.
Opportunity fix of an unrelated build error.
Closes#1408
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.
