Revert "Change ObjectIdUpdater interface to be more fluent"

This reverts commit 709d8ff3862fcbf6b3bc742030145d29134e2724.

Conflicts:

	src/main/java/org/jongo/PojoUpdate.java
Polish ObjectIdUpdater tests
Valid _id field type in FieldSelector
Check if type is oid compliant
Add check when trying to erase a Objectid with a new one
Add save tests
Support POJO without ObjectId mapped during insertion