GUI fixes

- Settings now a drop-down menu, new option 'CKAN settings' replaces the
old one
- KSP command-line options now under 'Settings'
- Fixed a bug where the mod list columns wouldn't get resized properly
on repo update
- KSP executable path now configurable from 'KSP command-line'
Implemented 'install suggestions' dialog
fixed tab lock during install
popup error message on exceptions
Refresh now issues a re-scan
Fixed incorrect download speed bug
Merge pull request #452 from AlexanderDzhoganov/master

Some GUI stuff