Fix version

[skinkie]

This attempts to fix the issue #455.

Choices made:

1. A Version element MUST exist in any file that uses versions.
2. version="any" cannot be supported unless a Version with version="any" exists.
3. This likely breaks a lot of examples too, so it is based on the other dataSourceRef branch.

[skinkie]

@ue71603 still too many examples that should be fixed first.

[Aurige]

see my comments on #455
Also I don't agree with "version="any" cannot be supported unless a Version with version="any" exists." : "any" mean that you can refer to any version you got (having a version number or not).
But I would agree that an object defined with an id and a version="any" does not really mean anything (but it's harmless, and could be seen as an explicit mention to say that the provider does not manage versions)

[skinkie]

It is not harmless. Especially because "any" has semantics. A default value specifically stating there is no version would work, since it hopefully wouldn't break constraint checking. And please don't suggest a "version number" NeTEx expectly doesn't have a version number, otherwise the version-attribute should not be a string.

[ue71603]

@skinkie @Aurige check the last commit. I worked on two examples and this adds layers that I am not sure, if they are good. Also "any" is NOT interpreted as it should. I had to add Datasource with id and version="78" to make it work.

[Aurige]

It still looks weird to me (the version of a version, and with Id=version as attribute) it can be a convention, but does not really mean something and can be misunderstood... I personally would really prefer things like <Version id="78"> for versions. Also defining a version with just an Id looks like a useless technical artefact to me: the version element was initially created to carry some semantics, not just to hold an Id.
This said, I agree that we need to clarify the semantic of "any"

[ue71603]

@skinkie will update this as we changed stuff already.

[ue71603]

@skinkie should I fix it before you start working? or will you do it anyhow?