Simplified code organization

A different mechanism now implements the syntax a() for emitting molecules with Unit values; no more auxiliary classes E, BE, EB, EE, which simplifies code and eliminates the need for whitebox macros. Breaking change: timeout(value)(duraction) instead of timeout(duraction)(value) as before. An optimization for the reaction scheduler now makes simple reactions start faster. The project build has been revamped: now there is a single JAR artifact and a single SBT project for JoinRun, rather than 3 as before. A skeleton "hello-world" project is available in a separate repository. Chymyst has been moved to a separate repository as well. Various improvements in the compile-time analysis of reactions: livelock detection now understands that molecules emitted under if/else constructions are not always emitted.