Split values into messaging and formatting

[BenediktBurger]

In #784 the question arose, how to modify the message formatting (due to a binary protocol) of values while keeping the messaging (ask of the instrument or channel, respectively).

Some parts of the message formatting of values may cause problems. For example the stripping of white space chars may corrupt a binary string, as a byte might have the value of a white space char by chance.

An instrument and a channel use different ask methods (either through the adapter or the instrument), therefore, the values methods have to be different too.

Several solutions were discussed in #784.
For example values could be split in a messaging part (ask) and a formatting part (the rest).