Remove unused signature features

[Mike-M0]

Describe your changes

• only create xmldsig fragments which are listed (like other fragments)
• remove unused fields for optimization (e.g remove "shall not be used" from standard) removed elements are not in structure and will result in en/decoder error NOT_IMPLEMENTED when "isUsed" flag is set or element is accessed in decoder.

Issue ticket number and link

Feature request #75

Checklist before requesting a review

• [x] I have performed a self-review of my code
• [x] I have made corresponding changes to the documentation
• [x] I read the contribution documentation and made sure that my changes meet its requirements

[Mike-M0]

The change is not optimal. I needed a manual change of eventCode in xmldsigFragment en/decoder from 1 to 32 and bitcount from 1 to 6 (which are the values from before this feature), because all other eventcodes are getting optimized out. I could not find a easy way to implement this in generator. But with this manual fix, PnC works fine again.

[barsnick]

Notes for us when reviewing this:

• Can this or should this be configurable (on/off)?
• Does it affect the API?
• Does it affect the ABI?
• Is it free of regressions?