Install script adds menu item, desktop icon, file association for
the current user - even if the Arduino installation was placed
outside of the user's home dir (such as in /opt or /usr/local).
Added three more icon resolutions (64px, 72px, 96px) - by using
the 256px file - maybe there is a better source available for this...
Modified build.xml for copying the existing icons and mime.xml file,
both scripts and adjusted file permissions (ugo+x) for *.sh files to
be executable by others by default.
