Adds Pandoc processing of include files for the Tools Developer Guide.
Checks-in the includes as rst files. The build.sh script will test the checked in versions in the repositories (local or remote)
and if necessary, update the checked-in versions.
Modifies the conf.py to exclude the _includes directory from Sphinx processing.
Modifies the CSS for the HTML to include formatting for a fifth level of title.
Changes the Tools Developer Guide title levels (and adds the includes) to work with the Pandoc-generated rst files.
Added options and usage for controlling if the includes are tested with local copies or remote.
Fixes for comments and formatting.
Update cached files.
Merge branch 'release/2.5.0' into feature/r2.5.1_ingest_clients
Fix build script to correctly use the remote clients includes files, and update the cached versions.
Set default for build script to be remote rather than local.
Merge pull request #524 from caskdata/feature/r2.5.1_ingest_clients

Adding ingest and authentication clients READMEs to the developer docs