fixed issue #14
added fest-swing-junit to dependencies to support synchronous swing testing
added testcase that checks if MainUI is handling focus properly
fixed checkstyle violations
adapted to pull request #12
starting the game via the GUI instead of direct programmatically
Added button names
Class is now actually using the button names
Merge pull request #19 from gewoonrik/v5.6-snapshot

Fix for issue #14 (incorrect tab/focus handling) with test case.