`Control` class: Common response function names

With the advent of new widgets such as `icon_widget`, a clear need has arisen for common function naming schemes for the `Control` class. The objective is so that the main event handler can use a common approach for calling multiple widgets to respond to various input events.

Of course, widgets aren't required to conform to any pre-defined response functions, but it will likely make it easier to write a Main loop event handler if widgets have the same function naming and a common expected effect.

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Here's one example. Looking at the [PyGUI](https://www.cosc.canterbury.ac.nz/greg.ewing/python_gui/version/Doc/index.html), it defines responses to [four mouse events](https://www.cosc.canterbury.ac.nz/greg.ewing/python_gui/version/Doc/event_handling.html):
- mouse down
- mouse up
- mouse drag (button is pressed)
- mouse move (button is not pressed)

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**This issue is raised to gather suggestions for the basic response functions to use in the `Control` class.**

Let's discuss a few basic functions that make sense in a touch environment on small microcontroller screens. The objective is not to collect 100% of cases, but to capture the few things that would be most used, and then grow from there.

Beginne mit der Durchsicht des Kontexts der Klasse Control, des Beispiels icon_widget und der im Issue verlinkten Referenzen zur Ereignisbehandlung von PyGUI. Die Arbeit ist abgeschlossen, wenn die Diskussion eine Einigung über eine kleine Gruppe gemeinsamer Namen für Touch- und Mausreaktionsfunktionen sowie deren erwartete Auswirkungen auf den Hauptereignis-Handler erreicht.

Vom Indexierungsmodell aus dem Issue-Text verfasst.