Build infrastructure adjusted to new LF repository structure

[a-sr]

• Updated LF submodule
• Adjusted build configuration in Maven and Eclipse
• Added mock classes that provide Kotlin-based classes for live runs. (This only affects live runs and debug runs from within Eclipse, not the final product, which will contain the real compiled Kotlin classes.)
• Fixed problem with URI access (requires Adjustments for running the LF compiler in Epoch lingua-franca#1844)
• Fixed compiler error detection in tests
• Fixed code in FederatedHelloWorld

[lhstrh]

Good idea to introduce these mock classes. Much better than the injection we were doing in the main code base...

[lhstrh]

I don't really understand what you did here. What is the point of these changes?

[a-sr]

I need to check whether there is an error during compilation but I don't want to parse the output of the compiler. Hence, I supply the compiler with a special error reporter to hook into the error handling. In the previous version, the occurrence on an error directly raised assertion error but it turns out the compilation is running in a separate thread, so JUnit does not notice the error and reported a successful test, even if the compilation failed. Admittedly, the new version is not perfect, but now it sets a static field to file the error in the compilation and then the JUnit test checks that field to raise an assertion error there.