Correct reference to supplementary documentation and make it available online

[kleihan]

V1.0 points to supplementary documentation for repository and interfaces as follows:

See the separate document “FixRepository2020.html” for a detailed technical reference for the Orchestra and Repository XML schema.

See the separate document “FixInterfaces2020.html” for a detailed technical reference for the Interfaces XML schema.

The filenames have changed to simply "repository.html" and "interfaces.html" and are contained in the folder "informative" in this GitHub repository. The two files should be made available online and the links in the spec clickable.

[kleihan]

Alternative is to remove the references and not provide the artefact online (it can remain in this repository in the "informative" folder). The Orchestra spec should be self-contained, i.e. not need a second document to use Orchestra.

[kleihan]

Changed names in V1.1 RC1 markdown