solve revision file fetching issue

Resetting size and saving to get a media file id created more issues
than it was solving. It might actually be a good idea to just skip all
log entries without a media file id associated because those are
*probably* not-so-interesting-entries.

Otherwise, the whole workflow needs some more thinking.
web player: add flash fallback
update composer dependencies
player: fix issue with empty chapters
improve chapter cache invalidation
improve logging display
globalize template autoinsert setting
improve migration workflow

fixes #82