Travis: Start xvfb for GUI tests.

Tested on #498.
Closes #499.
Catch authentication error with https.

Change the catch logic to throw a MissingCertificateKraken in the case of authentication failure ("System.IO.IOException: The authentication or decryption has failed.").
Show error message for missing certificate in the GUI.
Fix #505
Merge pull request #503 from pjf/nunit_gui_tests

Travis: Start xvfb for GUI tests.
Merge pull request #504 from mgsdk/certificate-fix

Certificate fix
Small fix to get our changes after InitializeComponent();
Fix mod list column resize on first repo update
Merge pull request #524 from AlexanderDzhoganov/fix_modlist_first_update

Fix mod list column resize on first repo update
GUI stuff, check description

- Better wrapping for the mod description
- Mark all updated button now greyed out if no updates are available
Better display of provided modules
Merge pull request #522 from AlexanderDzhoganov/505_dialog_size

Fix form scaling issue on linux (#505)
Revert "Catches DownloadErrorsKrakens gracefully"

This reverts commit baaf92f561f4d2c2f010f3876dc44d21e8aff728.

See discussion on #520 as to why.

Opens #368.
Merge pull request #525 from AlexanderDzhoganov/small_gui_fixes

Small GUI fixes for 1.2
Tested on windows.
Changed the tree transversal in MainModInfo to be breadth first instead of depth.
See #448.
Changing RelationshipResolver to use breadth first search.
Merge branch 'master' of https://github.com/KSP-CKAN/CKAN into #448