Create/use two extended value-strings & do other minor changes.

Create/use two extended value-strings & do other minor changes.

- Use VALUE_STRING_ENUM/VALUE_STRING_ARRAY macros to create one of the
   value string arrays instead of using the usual separate #defines & array definition;
- Remove a few unneeded initializers;
- prefs_register_protocol() need not be called under 'if (gp_zbee_prefs == NULL)'
- Do some minor whitespace changes;
- Add editor modelines.

Change-Id: I33669b25fa18ecc452b83a0d88a6c0b33aae904a
Reviewed-on: https://code.wireshark.org/review/441
Reviewed-by: Bill Meier <wmeier@newsguy.com>
Tested-by: Bill Meier <wmeier@newsguy.com>