Don't process --game_data if its value is empty

Closes #418
Merge pull request #437 from dorkster/bugfixes

Don't process --game_data if its value is empty
Ignore speed effects when adding hero power cooldowns
Merge pull request #439 from dorkster/bugfixes

Ignore speed effects when adding hero power cooldowns
Merge remote-tracking branch 'upstream/master' into keyboard_input