Refactor ExecutionContext, RuntimeService, etc. to clarify t heir semantics and handling of global state and code.

[vinjana]

ExecutionContext has much too much functionality for a single class.

Needs to be split up into multiple classes.

• File IO (directories, files, locks, buffers) only because of logging needs. Keep it with FileSystemAccessProvider.

• Loggging using standard logging framework removes the need to centralize here.

• On the other hand, keep global state, like BEJob states and executed jobs and commands here (for now).

• Overall, clarify the exact purpose of RuntimeService, ExecutionContext, FileSystemAccessProvider, Configuration and

• clean up all the mess!