Created a specialization of the eina::accessor for C++ Eo wrappers.
Created an override of the "accessor" methods in the eina::list specialization
for Eo wrappers (in eina_list.hh). It is necessary to create accessors with the
correct type.
Created specializations of std::is_base_of to avoid compilation errors related
with _Eo_Opaque type.
Added new test cases in "eina_cxx_test_accessor.cc" to test the accessor
specialization.
Added efl::eina::eina_init to the existing test cases to correctly do the
on demand initialization required by the tests.
@fix
Vitor Sousa
Savio Sena