Added single-click functions and events.

Added functions and events to enable single- and double-clicks to be identified. Now a program can allow a single-click to do one thing and a double-click to do another, without the double-click being preceded by a single-click event.

Added Double-Clicker Buttons

Added double-clicker buttons to the available features.
Updated AbleButtons test harness.

Refactored able-buttons to AbleButtons

The Arduino Button Library Extension (ABLE) is a simple, lightweight button library to capture input from buttons connected to the Arduino. AbleButtons supports debouncing buttons, basic button presses, held buttons and idle buttons, button clicks and callback functions. AbleButtons supports managing list of buttons together. Both pulldown and pull-up resistor circuits are supported. AbleButtons minimises its memory requirements through choosing a button class at compile time. A 'using Button = AbleButton' style command in your code includes just the features needed in your program.

Initial version

Initial version of the Arduino Button Library Extension (ABLE)