Improve image file resolution in thumbnails.
Better debugging
SSL and general URL scheme handling

* Forcing SSL URLs when possible
* Stripping URL scheme to default to current one, when possible
(http[s]://blah.com -> //blah.com)
* Changing plugin version value to have localStorage cache be updated
at next run (new i18n strings, new URLs shemes to be refreshed and
recached on next user run)