Added CeylonTaskListener to be notified of module compilation for ceylon/ceylon.language#488
CeyloncTool: make sure we use the right Log for ceylon/ceylon.language#488

Otherwise it was set to its default before we could set it to the user-specified one
Timer: log on Log for ceylon/ceylon.language#488
CeylonEnter: moved code to locate error node to typechecker for ceylon/ceylon.language#488: Ceylon embedded runner

So it can be reused in JS compiler
CeylonClassLoader: docs
Tests: moved non-caching class loader to ceylon-common for ceylon/ceylon.language#488: Ceylon embedded runner
CompilerTest: update for ArtifactResult.getRepository for ceylon/ceylon.language#488: Ceylon embedded runner
CeyloncTaskImpl: unset env.class.path so that we never use it for ceylon/ceylon.language#488: Ceylon embedded runner