Suggestion to move "uri" attribute from Classification to ClassificationType

[rubendel]

In requirements you can specify a "uri" for classifications, for example a URI pointing to a bSDD classification. In the current schema (0.9.6) this seems not possible for classifications in the applicability section (because there it is linking to Classification, which only has "value" and "system"). Here it can be equally useful.

My suggestion would be to move the "uri" attribute from Classification to ClassificationType