Code Signing support for CMake

Adds code signing support to CMake build scripts via the use of several functions and programs.

Usage:

codesign(CERTIFICATE 'certpath' PASSWORD 'password' TARGETS 'target[;target[;...]]')

CERTIFICATE

Required. Must hold the path to a valid certificate, or the build will fail.

PASSWORD

Required. Must hold the correct password for the certificate, or the build will fail.

TARGETS

A list of targets to enable code signing for.