Respect :unique_index option in #belongs_to

This simply passes the :unique_index passed to
#belongs_to on to ManyToOne#source_key_options

I have no time for refamiliarizing myself with the
testsuite, but it works for our app.
Add NamingConventions::Field::FQN

Given

* a model with storage_name = ‘accounts’
* a property with name = ‘name’

returns ‘account_name’

This is useful for defining database schemas which need minimal
renaming for natural joins
Merge remote-tracking branch 'origin/release-1.2'

Conflicts:
	lib/dm-core/associations/many_to_one.rb