Add unit test to check adding station
Add unit test to check adding station

Version 0.2 results in an error when a non-privileged user attempts to
add a station when ENHYDRIS_USERS_CAN_ADD_CONTENT is True. This version
did not have the problem, but we bring the unit test anyway.

openmeteo/enhydris,aptiko/enhydris,ellak-monades-aristeias/enhydris,openmeteo/enhydris,kickapoo/enhydris,kickapoo/enhydris,openmeteo/enhydris,ellak-monades-aristeias/enhydris,kickapoo/enhydris,aptiko/enhydris,aptiko/enhydris,ellak-monades-aristeias/enhydris