hook: add support for X-Aiaiai-Project

hook: add support for X-Aiaiai-Project

Rather than determining the project strictly from the +project portion
of the aiaiai address, also allow the dispatcher hook to insert the
project hook into the mbox header. This could be used to allow advanced
configuration of the project, such as by checking patch diffs to see
which files are modified.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>