Docs have moved from min.io/docs to docs.min.io/commuinity.
This fixes hard, external links to use the new subdomain.
Note that some of these files are automatically pulled from elsewhere as
part of the build process, so some may not carry through even after this
PR merges.
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.
