Add sqlalchemy migration utils.create_shadow_table method
Add sqlalchemy migration utils.create_shadow_table method

This method allows to create shadow table by existing table.

Two use cases:
a) create shadow table by table name
b) create shadow table from table instance

blueprint db-improve-archiving

Change-Id: Ib3a3797782b89a9a89baa60738edcabde7fe1299

n0ano/ganttclient