Add support for double taps etc

[KaneCheshire]

This can just be more functions on Tappable, with default implementations that InteractionContext can use to create new functions.

I'm thinking we should support:

• Double taps
• Long presses (with configurable durations as a parameter)
• Two finger tap

Since these are already functions on XCUIElement it should be trivial to add support and make them BDD-y.