Change Relation Macros

Change the relation macros for referenced associations for better compatibility with gems geared towards Active Record.

:referenced_in => :belongs_to

:references_many => :has_many

:references_one => :has_one

:references_and_referenced_in_many => :has_and_belongs_to_many

Also remove all the previous aliases for a consistent API.

This is backwards breaking, marked for 3.x