Allow to hide tool bar only from preferences
Keep alternate background when adding and removing items

Items keep their background style when inserting or removing any items
on previous rows.
Focus first output item from command if selection is not changed
Option to change application language
Defer language combo box initialization
Ask user to cancel exiting if some commands are still active
Merge pull request #131 from rygwdn/mac-support

Add support for OS X
Updated list of developers in AUTHORS file and help dialog
Fix condition for asking user to cancel running commands
fix bundling of plugins on OS X.