Allow all applications to be headless

We disallowed applications which we don't have in a static list to run as headless when we
were still using a the webapp launcher approach. Now with a real webapp manager which can
control how much memory is used per application this is not a big problem anymore and we
can enable it again to improve our compatibility with legacy webOS.

Signed-off-by: Simon Busch <morphis@gravedo.de>