Remove symlink site -> site-modules

The symlink served for a good discussion point around change impact, but
in the end having it makes for a more confusing experience overall both
to new users cloning the control-repo to get started and also to anyone
accustomed to "site". A new user won't miss "site". A symlink will muddy
the waters over the change for long-time users. Better for clarity to be
all-in and not include a symlink.

Author: reidmv