Some small touch-ups to plug-in code
Some small touch-ups to plug-in code

- Use stdlib's 'pathname' to make file path manipulations slightly
  more concise.
- Add some missing comments.

Change-Id: I1da958ce7c5f528628ab3b706229b7de7f16ec62

stuartbman/mediawiki-vagrant,wikimedia/mediawiki-vagrant,HarriAlasi/wiki3dviewer,HarriAlasi/wiki3dviewer,HarriAlasi/wiki3dviewer,ankita-kumari/mediawiki-vagrant,stuartbman/mediawiki-vagrant,stuartbman/mediawiki-vagrant,ankita-kumari/mediawiki-vagrant,HarriAlasi/wiki3dviewer,huit/mediawiki-vagrant,HarriAlasi/wiki3dviewer,physikerwelt/DRMF-vagrant,huit/mediawiki-vagrant,stuartbman/mediawiki-vagrant,stuartbman/mediawiki-vagrant,wikimedia/mediawiki-vagrant,wikimedia/mediawiki-vagrant,ankita-kumari/mediawiki-vagrant,stuartbman/mediawiki-vagrant,ankita-kumari/mediawiki-vagrant,HarriAlasi/wiki3dviewer,wikimedia/mediawiki-vagrant,huit/mediawiki-vagrant,physikerwelt/DRMF-vagrant,ankita-kumari/mediawiki-vagrant,HarriAlasi/wiki3dviewer,huit/mediawiki-vagrant,wikimedia/mediawiki-vagrant,physikerwelt/DRMF-vagrant,wikimedia/mediawiki-vagrant,stuartbman/mediawiki-vagrant,physikerwelt/DRMF-vagrant,huit/mediawiki-vagrant,ankita-kumari/mediawiki-vagrant