Policy checker: initial version

Policy checker: initial version

Policy checker is based on Schematron, which allows writing
declarative checks for xml files (see rules.xml file for details) and
yields xml output (which is converted to plain text for readability, but it
can be converted to any format). The checker is a shell script, it
depends only on xsltproc (libxslt-tools package in Tizen), so it's very
lightweight.

We can run the checker on any single dbus configuration file, e.g.:
./check ./test-policy.conf (a test policy containing violations of all
the implemented rules). So, during a package installation we can run
the checker on it's dbus configuration file.

Change-Id: I523b7a730fc93a0d4f99bc8ba750be7b6f0e051c