Fix AliasGroup equality + add extra tests
Merge branch 'master' into 1.0.x
[WIP] Legacy code removal

This commit tackles the initial part of two distinct though related tasks:

* Removal of the old serialization and deserialization code.
These are the toArray and newFromArray methods.

* Swicthing Entity, Item and Property over to contain value objects
rather than the internal serialization format.