Bdd read contenttypegroup

Depends on:
> ezsystems/ezpublish-community#131 - changes from protected/private methods to public to be accessible  from the sub contexts
ezsystems/ezpublish-community#137 - enable REST test (without this the rest is not actually being tested)
ezsystems/ezpublish-kernel#827 - base implementation of rest and ContentTypeGroup
ezsystems/ezpublish-community#136 - needs ValueObjectHelper
ezsystems/ezpublish-community#135 - the ContentTypeGroup given steps are also needed to test this
ezsystems/ezpublish-community#139 - minor change on error sentences

To do::
- [x] Add feature file
- [x] Add sentences definitions to interface
- [x] merge ezsystems/ezpublish-community#131
- [x] merge ezsystems/ezpublish-community#137
- [x] merge ezsystems/ezpublish-kernel#827
- [x] merge ezsystems/ezpublish-community#136
- [x] merge ezsystems/ezpublish-community#135
- [x] merge ezsystems/ezpublish-community#139