Merge pull request #614 from AlexanderDzhoganov/master

Small GUI ModList touch-ups
Merge pull request #615 from AlexanderDzhoganov/master

Re-enabled repository selection for the GUI
Added Net.UserAgentString which all WebClients will use
Can set user-agent through cmdline with --net-useragent
Added --net-useragent to NetKAN
Merge pull request #616 from AlexanderDzhoganov/612_webclient_useragent

Code looks good, Travis is happy, engage.....

and I hope that my PR will merge cleanly :)