Move kitrap0d exploit from getsystem to local exploit

This version modifies the existing meterpreter session and bumps the privs
up to SYSTEM. However it's not how local exploits are supposed to work.
More work will be done to make this create a new session with the elevated
privs instead.
Add extra URL for exploit detail
Initial environment config for development
Restored database.example
added OSX module screen_capture
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.
General improvements addressing feedback
Changed option SNAP_FILETYPE to FILETYPE
Various tidies and fixes

* Change ranking.
* Update references to comply with correct approach.
* Update messages to better describe what should happen.
* Update the Windows version regex to match XP.
* Update `check` function to use `unless`.

Thanks again @jvazquez-r7 for the feedback!
Work in progress
Modified module to use windows/screen_spy code
Tighter error handling
Removed unnecessary delay
Add Win 8 to constants
Bump version number since 4.8.0 is out
Add a spec for version checking.
Don't be dopey in the RSpec version matching
Land #2637, version number bump to 4.9.0-dev
Update class for Win 8
Clean screen_capture