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
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.
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!
Remove genericity, x64 and renamed stuff

As per discussion on the github issue, the following changes were made:

* Project renamed from elevate to kitrap0d, implying that this is not
  intended to be a generic local priv esc exploit container.
* Container DLL no longer generic, always calls the kitrap0d exploit.
* Removal of all x64 code and project configurations.
* Invocation of the exploit changed so that the address of the payload
  is passed in to the exploit entry point. The exploit is now responsible
  for executing the payload if the exploit is successful. This removes
  the possibility of the payload getting executed when the exploit fails.
* Source moved to the appropriate CVE folder.
* Binary moved to the appropriate CVE folder.
* Little bit of source rejigging to tidy things up.
Updated meterpreter binaries

Includes the following:

* Clean builds
* Removal of kitrap0d from getsystem
* Doc updates
* Webcam crash fix
* Schedular and channel refactor
* Posix crash fix for post modules
Land #2640, @OJ's updated meterpreter binaries
https://github.com/rapid7/meterpreter/commit/0012c4530aaa3fa176e393b8475358ed0682c759
Land #2633, @OJ's port of Kitrap0d as local exploit