sqlalchemy: default mysql parameters for db.Table
sqlalchemy: default mysql parameters for db.Table

* Adds default parameters to `db.Table` constructor to force MyISAM
  engine for MySQL backend. db.Table is InnoDB by default on modern
  versions of MySQL. Hence, foreign keys can now be set on
  `db.Model` fields because both are using MyISAM as an engine.
  (closes #2491)

Signed-off-by: Artem Tsikiridis <caaedba182ed971d1251b28968931a7d2c504eb3@cern.ch>
Reviewed-by: Gilles Louppe <eab2041f1da7b9758df303675fa51d3c0b26d877@cern.ch>

tiborsimko/invenio,inveniosoftware/invenio,inveniosoftware/invenio,tiborsimko/invenio