Unify toolbox restorecon and libselinux restorecon implementations.

Extend the libselinux restorecon implementation to allow reuse
by the toolbox restorecon command.  This simply requires adding
support for the nochange (-n) and verbose (-v) options to the
libselinux functions and rewriting the toolbox restorecon command
to use the libselinux functions.   Also add a force (-F) option to
support forcing a restorecon_recursive even if the restorecon_last
attribute matches the current file_contexts hash so that we can
continue to force a restorecon via the toolbox command for testing
or when we know something else has changed (e.g. for when we support
relabeling /data/data and package information has changed).

Change-Id: I92bb3259790a7195ba56a5e9555c3b6c76ceb862
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>