Fix cluttered nzbget log

Every time nzbget checks rss, it (depending on web server) complains about missing Content-Length header even though it is not mandatory HTTP header (according to RFC). Already reported upstream: http://nzbget.net/forum/viewtopic.php?f=3&t=930#p7564
Update tt-rss to 1.13
Update selfoss to 2.11
Add site config files to full-text-rss
Merge pull request #2 from SynoCommunity/develop

update