Initial commit of the Bourne shell command stager, nothing uses it yet.
include the new mixin
fix for OSX and remove unnecessary lines
list valid DECODER values and add the sshexec module
escape ticks and spaces in paths
change DECODER OptString to OptEnum per egypt's recommendation
allow the mixin to auto detect an available decoder binary
Revert "escape ticks and spaces in paths"

This reverts commit 4c87b1ba3650c286fa9721b0fd6e0c0937cc9a9c.
Remove the DECODER option
Condense the decoder commands
Landing #1275, bash cmdstager

Conflicts:
	lib/rex/exploitation/cmdstager.rb

Conflict was just the $Id$ tag, which is no longer used anyway.