docs: update admin-guide/interface.rst to use Sphinx menuselection and guilabel roles

Change-Id: I3ebf771d3a9c823ff11d8f72deeee2d5c4caeb7f
docs: admin docs for adding/editing external reports

Change-Id: I030ab36caf474b7c83fb64e73847319248f3c585
docs: admin docs for editing OS versions

Change-Id: I409870db6c7ffec56de8d0f77f882508fdfa18d7
docs: start of a task-oriented section in the admin guide

For now just has one task, for setting the newly supported
per-OS-version install options.

Change-Id: I1fd435a1a5fff0729a966eaa7e34c285a6ea4aaa