fix issues which occur with multiple IntelliJ windows

- ui components may not be a singleton (one instance per window required)
- action groups created from config may not be modified directly (copy required)
fix Gerrit checkout in case of empty settings

- password needs to be preloaded in UI thread for async tasks

Resolves #46
bump version to v0.6.1-SNAPSHOT

- update changelog
- update copyright year
Merge remote-tracking branch 'origin/master' into intellij13