Add StorageObj instantiation without schema
Add StorageObj instantiation without schema

    * An 'StorageObj' needs an schema with ClassFields to define its content.
      But at instantiation time... it should not be needed. Therefore a user
      can issue: " x = StorageObj('persistent_object')" and Hecuba would
      reconstruct its content. The rationale behind this is to be consistent
      with 'StorageDict', where this was also possible.

    * In order to reconstruct the 'StorageObj' a new field 'columns' is added
      to 'hecuba.istorage' with the metadata needed (the attributes' names and
      types).

    * Rewrite the __init__ and _store_meta methods

bsc-dd/hecuba,bsc-dd/hecuba,bsc-dd/hecuba,bsc-dd/hecuba