fix Linux installers

Move the "lookup R home" trick out of the forwarding executable,
so that it no longer relies on the vtksys shared library.

Call fixup_bundle on all platforms (not just Mac).  This removes
the need to manually install the Qt libraries (fixup_bundle takes
care of it for us).
Merge branch 'improve_installers'

* improve_installers:
  fix Linux installers
Merge branch 'master' of git://visomics.org/visomics