Finalise the local exploit for kitrap0d

The exploit now properly injects the DLL using RDI and invokes the
exploit based on a parameter passed by the Ruby module. The elevate
code is 'generic' with a goal of possibly supporting more exploits
down the track.

New sessions are now created with the SYSTEM creds, rather than
modifying the existing session. This is now inline with how things
are done with other local modules.