removed wildcard handling to fix #71

Following the discussion from #71 here are the changes:
- disabled wildcard handling in Obis identifier comparison.
- added stricter handling on parsing codes to throw an exception if hex codes are used or invalid numbers.
- default Obis constructor now initializes with 0xff to be more in line with string parsing. 
- some more unit tests for obis
- added exception handling for MeterD0 around Obis string parsing. Invalid values will just be ignored but parsing continued. Later we could remove the strong restriction to only allow obis_codes starting with 1 or 2 (especially since all EDIS meter will report 255....) but somebody with a Landis&Gyr E350 needs to test this first.

I tested with my Hager EHZ361 and had no issues and no need to adjust my config file.
Please do intensive testing and let me know any issues.
No this should be fine. I double checked with two more units tests.
Anyhow I changed it to be easier readable to
return *this == Obis();

> Am 26.12.2014 um 12:40 schrieb andig <notifications@github.com>:
> 
> In src/Obis.cpp <https://github.com/volkszaehler/vzlogger/pull/78#discussion-diff-22282546>:
> 
> > @@ -255,15 +264,8 @@ bool Obis::operator==(const Obis &rhs) const {
> >  	return 1; /* equal */
> >  }
> >  
> > -bool Obis::isNull() const {
> > -	return !(
> > -		_obisId._raw[0] ||
> > -		_obisId._raw[1] ||
> > -		_obisId._raw[2] ||
> > -		_obisId._raw[3] ||
> > -		_obisId._raw[4] ||
> > -		_obisId._raw[5]
> > -		);
> > +bool Obis::isAllNotGiven() const {
> > +	return operator==(Obis()); // compare this one with empty one
> Change == to ==?
> 
> —
> Reply to this email directly or view it on GitHub <https://github.com/volkszaehler/vzlogger/pull/78/files#r22282546>.
> 

Gruß

Matthias Behr