0.19-beta released

Community-authored maps may now be downloaded from the main screen without any server login required.
Auto-synthesize option, accessed from new 'controls' dialog: when enabled, catalysts synthesize their compound without requiring a double-click.
Unapproved / submitted maps can optionally be set to "hidden" which means they may only be downloaded if the player knows the map name.
Certain 'quit' buttons, and other buttons renamed / reorganised
Some keystrokes rationalised