[POC] Split property selection from graph navigator

[goetas]

Q	A
Bug fix?	no
New feature?	yes
Doc updated	no
BC breaks?	yes
Deprecations?	no
Tests pass?	no
Fixed tickets	-
License	MIT

This changes a bit the way how the serializer internally works. The solution is still ugly and does not work (yet) but has big potentials.

With this implementation:

• the property selection depends only on the current exclusion strategy, and since the exclusion strategy does not change during the whole graph visitor, can easily be cached (and even compiled for group/version based exclusion strategies)
• the property access depends only on the class metadata and can be easily compiled into static classes. in addition now the property access can be done in batch, using a single closure for property access (compilation ca be easily done using symfony expression language)

Feedback (and help) is welcome