Add a unit test for providing an alternate rules loader that also
demonstrates how users can define sub-classes that may want to extend
the falco rules syntax.
This test creates a test rules reader/collector/compiler that supports
top-level objects "test_object". The reader reads them and saves them
in the collector. The compiler iterates over all test_objects and puts
the property values into a single set<string>.
Signed-off-by: Mark Stemm <mark.stemm@gmail.com>
