Revision 1366

* Thuban/Model/transientdb.py (TransientJoinedTable.__init__):
Update doc-string
(TransientJoinedTable.create): Do not modify the column objects of
the input tables in place and copy all columns of the input tables
into the joined table after all.

* test/test_transientdb.py
(TestTransientTable.test_transient_joined_table_same_column_name):
Update to reflect the new behavior
(TestTransientTable.test_transient_joined_table_with_equal_column_names):
Update to reflect the new behavior
(TestTransientTable.test_transient_joined_table_name_collisions_dont_modify_in_place):
New test case for a bug which modified the column objects in place