Add attribute mapping for user information

Add attribute mapping for user information

When user information is retrieved we map any wellknown data to a
standardized set of names.
A ne InfoMapping class takes cares of helping the info modules to
map the data they retrieve so that providers can find it in wellknown
attribute names for further use.
Mapping of attribute names for diplay purposes is also provided.

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