drawing-area: allow zooming in and out with keyboard

git-svn-id: https://micropolis.googlecode.com/svn/trunk/micropolis-java@762 d9718cc8-9f43-0410-858b-315f434eb58c
overlay-map: fix selection rectangle for non-default zoom levels

git-svn-id: https://micropolis.googlecode.com/svn/trunk/micropolis-java@763 d9718cc8-9f43-0410-858b-315f434eb58c
drawing-area: fix crash bug caused by not loading sprite images

git-svn-id: https://micropolis.googlecode.com/svn/trunk/micropolis-java@764 d9718cc8-9f43-0410-858b-315f434eb58c
drawing-area: fix where sprites are drawn when zoom level is not 16px

git-svn-id: https://micropolis.googlecode.com/svn/trunk/micropolis-java@765 d9718cc8-9f43-0410-858b-315f434eb58c
drawing-area: scale sprite images with tile resolution

git-svn-id: https://micropolis.googlecode.com/svn/trunk/micropolis-java@766 d9718cc8-9f43-0410-858b-315f434eb58c
drawing-area: fix so that keyboard zoom works even when a button has focus

git-svn-id: https://micropolis.googlecode.com/svn/trunk/micropolis-java@767 d9718cc8-9f43-0410-858b-315f434eb58c