Integrate ESCom specification

[dirk-qualisys]

As agreed with Cefic, the ESCom specification (in repository https://github.com/esdscom/escom-xml) will be integrated with the latest SDScom specification to form eSDScom 5.4.

This requires

• adding the appropriate data structure, but not any parts that ESCom takes from the SDS main body
• harmonizing the data types, which is mainly an issue for phrases which are specified with different features

[dirk-qualisys]

The naming of numeric types is taken from ESCom, plus more detailed type varietes are introduced, but due to the (as far as we know) larger adoption rate of SDScom, the internal structure of those types is taken from SDScom:

• The biggest difference is that units have to be provided as an enum and the phrase id is optional, while ESCom took a mandatory phrase ID and nothing else. However, if the phrase is there, the enum value should be possible to take from the phrase text (dirty solution - mapping is of course cleaner).
• Minor differences are field naming and lowercase qualifiers.