Enhanced longpress by adding longPressStart and longPressStop callbacks

This commit adds more fine grained callbacks "longPressStart", "longPressStop" and "duringLongPress".
The original "attachPress" methods and logic is kept in tact for backward compatibility, but can be deprecated.
For better readability, the term "press" could be changed to "longPress" throughout the code, since a click is also a press of a button, be it a short one. I did not make these changes yet, as they would make it less clear which logic has changed by this commit.