Add firefox platform, architecture, and payload.

* Enables chrome privilege exploits in firefox to run a javascript cmd
shell session without touching the disk.
* Adds a spec for the addon_generator.
Add firefox paylods.

* Adds support for windows or posix shell escaping.
DRYs up firefox payloads.
Fix comment.{
Reorder targets.
Kill unnecessary comment.
Update proto_crmfrequest module.
Digging around to get shell_command_token to work.
Rework windows shell to use wscript.
Minor cleanup of firefox.rb.
Fixes shell escaping errors with nested quotes in windows.
Add exec payload. Cleans up a lot of code.

Adds some yardocs and whatnot.
Whitespace tweak.
Refactor runCmd, allow js exec.

* Updates exec payload to not touch disk
* Adds XSS module that uses hiddenWindow (to avoid X-Frame-Options)
Update exec to be diskless.
Update firefox payloads to use async runCmd.
Use shell primitives instead of resorting to
echo hacks.
Fix description to be accurate.
Remove Java target, since it no longer works.
Fix bug in the firefox/exec payload.