yaml: add eve flow and netflow entries

Added, commented out by default.

Bug #1257.
output-lua: add script-dir config param

Add 'scripts-dir' config directive that is prepended to the script
names to form a path. If ommited or empty, script are opened from
the CWD.
output-lua: add config to yaml

Disabled by default.
output-lua: set proper callbacks for HTTP

Enable the relevant HTTP callbacks.

Bug #1287
flow: fix flow logging at shutdown

Move all flows from the hash to the recycler at shutdown.

Bug #1260
flow json log: add 'shutdown' as flow end reason

When engine shuts down all flows in the hash are logged out. They
may not have timed out yet. So they are forced. Log the reason to
be 'shutdown'.