rbt patch subcommand to support --print option
rbt patch subcommand to support --print option

This adds an option to print the patch to stdout instead of trying to apply it.
This allows more flexibility. i.e. in case the patching fails, or the user
wants to inspect without patching.

Reviewed at https://reviews.reviewboard.org/r/4525/

halvorlu/rbtools,beol/rbtools,reviewboard/rbtools,haosdent/rbtools,davidt/rbtools,beol/rbtools,datjwu/rbtools,1tush/rbtools,reviewboard/rbtools,beol/rbtools,datjwu/rbtools,haosdent/rbtools,haosdent/rbtools,datjwu/rbtools,halvorlu/rbtools,davidt/rbtools,reviewboard/rbtools,halvorlu/rbtools,davidt/rbtools