Fix null/undefined condition
Improved meta types organization

Removed 'primitive' type, and 'object' type from prototype.
Introduced 'prototype' type, and made 'object' type valid only for
prototype only extensions.
Introduced _childType_ for namespace, possible values are 'primitive'
and 'object'.
Logic cleanup
Do not create indexes on primitive ns
Replace protoDeep with type dedicated methods

It should now correctly adjust prototypes of relations and
relation set items
Cover properties of base relation set item as well
Improve comments
Dedicated getIndexKey function for value indexing
Fix indexes on prototype switch
Define relation label