Fixed:
▪ Some minor stuff fixes.
▪ Unnecessary "Welcome" notifications. (bug #176)
▪ Bad handling of null/empty strings when inserting messages into DB. (bug #169)
▪ Bad conversion of "created on" date/time in TT-RSS plugin. (bug #172)
▪ Missing obligatory attribute in OPML 2.0 files. (bug #166)
