Make available case insensitive mapping matching

If ignore_case is True then the incomping attributes are matched
case-insensitively in the policy engine.
The CAse of the incoming attribute is not changed on wildcard
matches. On ther matches attributes will be replaced according
to the mapping tables and the case used will be that of the
mapped attributes.

Signed-off-by: Simo Sorce <simo@redhat.com>
Reviewed-by: Patrick Uiterwijk <puiterwijk@redhat.com>