aaa: Introducing changes to REST-API (at domain groups and ids)

For domain groups/users the ids do not serve as primary
keys in db any longer.
Primary keys (internal ids) are generated by engine code.
The forma of the domain group/users ids is hexadecimal
represenation of the id in the domain.
At db users/db groups presentation this information is
presented as "domain_entry_id"

Topic: AAA
Change-Id: Iaecb5d43945769db82475edde1c7075c1a343c07
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>