fix: expect a 204 when updates are ignored in update or append attributes operations

See merge request !115

- calling Suite Teardown only cleans up data from last TC in the suite
- clearly identify setups steps in TCs
- prefer Set Test Variable when variable is set in a TC

- was the same as Delete Entity by Id keyword

- moreover, it was not deleted, which broke some subscriptions tests later

# Conflicts:
#	TP/NGSI-LD/ContextInformation/Consumption/Entity/QueryEntities/019_02_05.robot
#	TP/NGSI-LD/ContextInformation/Consumption/Entity/QueryEntities/019_05.robot
#	TP/NGSI-LD/ContextInformation/Consumption/Entity/RetrieveEntity/018_05.robot

fix: tests asking for GeoJSON representation

See merge request !113