Add a bit about adding, moving and copying files for patches.

Differential Revision:	https://reviews.freebsd.org/D1052
Reviewed by:	wblock
Sponsored by:	Absolight


git-svn-id: svn+ssh://svn.freebsd.org/doc/head@45950 c2e8774f-c49f-e111-b436-862b2bbc8956
Enhance the Poudriere chapter a great bit.

Differential Revision:	https://reviews.freebsd.org/D770
Submitted by:	riggs
Reviewed by:	wblock
Sponsored by:	Absolight


git-svn-id: svn+ssh://svn.freebsd.org/doc/head@45951 c2e8774f-c49f-e111-b436-862b2bbc8956