Handle ManyToMany relations in embedded lists

[rimi-itk]

Resolves #52

[coveralls]

Coverage decreased (-1.3%) to 90.024% when pulling 301bdf5 on rimi-itk:Issue-52 into dece12c on alterphp:master.

[alterphp]

Hi @rimi-itk !

It looks good. I merge into master, then write a test to avoid regression and then tag it.

Thanks for this contribution !

[rimi-itk]

Thank you! Sorry about decreasing the code coverage …

[alterphp]

code coverage will increase with the test, no worries. Anyway, code coverage is not a real quality indicator (what is covered is not necessarly tested).