Feature/rqes module

[n0900]

A bad attempt at seperating RQES related files into two modules rqes-data-classes and vck-rqes with the latter being a placeholder for additional services which may or may not merge with vck-openid depending on how pure we want to keep that module. This current version has the following short-comings:

• rqes-data-classes is a dependency for everything
• QesInputDescriptor should be in rqes-data-classes but is in dif-data-classes for serialization reasons
• SignatureRequestParameters should be in rqes-data-classes but is in oauth-data-classes for serialization reasons

Better ideas/improvements very welcome

[n0900]

Rebase to #149

[n0900]

This should now be a clean seperation of data modules and vck-rqes. I am not sure about CSCAuthenticationRequest yet but it is out of scope for this pull request and since it does not interfere with the current functionality I will deal with it in #127 or a seperate pull request.