This will allow to execute any file and detect it's type to handle it.
This will allow to use shell for bootp bootfile or dfu.

You can register multiple hook for the same filetype. They will be execute
in the invert order of register. If a hook does not handle the file you just
return -ERESTARTNOHAND;

This is only available with hush parser.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>