Added support for responses longer than 4 hex digits

[JakubDziworski]

There are PID commands that result in responses longer than 4 hex digits. For example 223277 code for opel insignia returns 6 hex digits response (kms since last dpf regeneration). I logged some variables when debugging the PID:

 query: 223277
 firstHeadIndex: 6
 secondHeadIndex: -1
 payload: 22327762327700000E
 header: 623277
 firstDatum: 12
 recBytes: 18
 payBytes: 6

As you can see the response should be 00000E (15km since dpf regeneration) but currently it returns 0000 since implementation is fixed on only two types of responses size (2 and 4 digits).

I added more generic implementation which reads everything from firstDatum till the end thus allowing any response size.

I've done some regression testing with multiple commands on opel insignia and found it works fine

Let me know what you think