Revert single value attributes parsing

[Krolken]

The XADRParser is now returning the value if an attribute is just a single value and a list of values if there is more values.
This made it annoying building a more general way reading alot of values.

It would be better if the function returned a list in either case. If it is a single value you will need to access the first element in the list instead.

[Krolken]

Actually this was harder than I thought.
Since we have APDU parsing dependant of the Parser in some spots it either made the code very unclean or broke apdu-parsing to get the correct handling.

It is a bit dependant on #26 since when the parser is no longer handling apdu-parsing we can cut alot of functionality and all the extra fluff that was added so that the parser could handle sequences of dlms-data to and just make a simple and pure parser for that.