FwImport - add more Gateway support

 
  - [ ] routing
  - [ ] interfaces
  - [ ]  GlobalPolicyUid
  - [ ] EnforcedPolicyUids
  - [ ] EnforcedNatPolicyUids
  - [ ] ImportDisabled
  - [ ] ShowInUI

#### also
consistent usage of null vs emptystring in different fields, like uids, names, etc (needs to be kept consistent in normalization from native config, when writing to database and when building config from db)