Add Classification support

[peter-lobner]

Adds support fro srmd classifications via an GElementCommont group that wraps annotations and classifications.
Therefore srmd classifications can be used with all entities that are annotatable.

[peter-lobner]

Documentation is currently missing

[pmai]

Can this (and the other PR) be redone so that there are actual clean diffs (i.e. no changes in whitespace and other formatting that makes the changes very hard to review and also impossible to merge as is)? It also seems to me, but again hard to check with all the superfluous changes, that this touches more places than it technically needs to.

Other than that this PR is misnamed: It does not add SRMD support at all, it adds classifications. SRMD is a stand-alone file format, not the SSP Traceability classifications.

I think that SSP should first add support for specifying per-element (and other entities, like parameter sets, ...) generic meta-data support, which could then be used to point to / embed SRMD files and other format meta-data.

That SSP might also want to add classifications for all modeling elements is I think another issue.

[peter-lobner]

Any ideas what formatting settings to use? I use XML Spy.

[pmai]

Any ideas what formatting settings to use? I use XML Spy.

Ideally tell XML Spy to not touch anything that you are not changing, and to use 4 spaces no tabs indentation. Not sure how to tell XML Spy this, I tend never to use it.

It is usually easier to work with editors in textual mode, as for any other language, as this allows clearer control of the stuff changed...

[peter-lobner]

I think that SSP should first add support for specifying per-element (and other entities, like parameter sets, ...) generic meta-data support, which could then be used to point to / embed SRMD files and other format meta-data.

That SSP might also want to add classifications for all modeling elements is I think another issue.

I think that can easily be incorporated in the current proposal.