Use Matrix Build for supported MPS versions

[coolya]

Right now it's quite cumbersome to maintain multiple MPS versions at the same time, especially since we match strictly against the complete MPS version with the plugins.

At least from a maintenance point of view it should be possible to build the "modelcheck" and "generate-models" plugins against all supported MPS versions in the same build step. Since they are already subprojects we could use gradle composite builds and dependency substitution to do this.