Add keda specific table for reservations

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Minor style fixes in models

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Make keda OneToOneField

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Remove keda fields from reservation admin

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Refer to Keda and not to Reservation

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Remove keda fields from reception

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Fix error message

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>