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* Added name attribute to DataTypes. This is mostly optional and not needed, but mandatory for elements of a struct.
* Changed cardinality of the occurrence of elements that are part of a list of elements (e.g. <Arg><Args>...</Args></Arg> from ?zero or more? to ?one or more? when the surrounding list element itself is optional* Added Constraints to DataTypes

- Changed tests accordingly

- Made DeviceInfo list optional.
- Added <Args> around list of <Arg> to be consistent with other lists

Fixed various examples.

- Moved <Doc> elements to the top of each element.
- Added <Doc> to <Domain>
- DeviceDef is now directly included in SubDevice
- Added structured DataType and renamed element name in using elements
- Added unitOfMeasure attribute to DataType

Applied changes for 2.0
Started on documentation