Table group joins support in hql

[bahusoid]

Loose port of hibernate/hibernate-orm@753858c

Example of SQL generated with "group joins":

SELECT *
FROM Person person0_
INNER JOIN (
	IndividualCustomer individual1_ 
	INNER JOIN Customer individual1_1_ ON individual1_.IndividualCustomerID = individual1_1_.Id
	) ON person0_.Id = individual1_.PersonID AND individual1_1_.Deleted = @p0

It's useful when withClause needs to be applied to multiple tables:

• subclasses with withClause referencing base tables
• Complex withClause with implied joins (like from a in A join b in B b on a.Id equals b.C.D.Id also see added test case WithImpliedJoinOnAssociation)
• Many-to-many with filters/ withClause (makes fix implemented in Fix #1994 (many-to-many filter in hql) #1995 obsolete as with group joins no null data is retrieved)

Fixes hql/Linq for #1209 and #1215

[bahusoid]

It's done! It's a good stuff :)