Detector tweaks

[denniswittich]

Motivation

In some projects we found the lazy worker to be problematic and prefer to implement the lazyness in the application code.

There was also a reconnection bug where the rosys-detector module tries to reconnect while the detector still thinks the connection is established. Problem occured when auto_disconnect is False and the detector container is stopped and restarted while the rosys container keeps running. This seems to be solved by explicitly calling disconnect before reconnecting.

Implementation

• make use of lazy worker optional
• enforce disconnect call after failed connection attempt

[falkoschindler]

Some thoughts about the event handling:

• I suggest to name the event handling callback using the imperative "handle_..." instead of "on_...". This way you can write, e.g., button.on_click(handle_click) which reads quite naturally.
• We shouldn't introduce new public methods that are only used internally. So the new event handlers should be marked as private.
• Instead of creating new methods we can keep using nested functions and only replace the decorators with the "method way" (which is actually not a method but a function).
• We can skip everything above and simply use lambda expressions. 😄