Put mux handling into I2CManager_NonBlocking.h to keep the native (controller-specific) drivers more simple.
Remove almost all but one of the static definitions, in preparation for supporting multiple I2C buses.
Two new drivers: PCA9685pwm drives the PCA9685 I2C device directly, and Servo driver which acts as a 'shim' over the top to control animations. This is aimed at supporting devices like the EXIOExpander by allowing the Servo driver to talk to the EXIOExpander driver instead, to animate servos on another controller.
AVR Native (non-blocking) driver now supports up to 8 I2C Multiplexers, as does any controller that uses Wire for I2C.
Other native drivers will be updated in due course.
To support a HAL Display driver, the SSD1306 driver can be created (new) and then the I2C address assigned explicitly in the begin() call. The original approach of looking for the I2C device address has also been retained in a different constructor.
Update I2C addresses of HAL devices to type I2CAddress (to support extended address functions).
Cast I2CAddress variables in DIAG calls to (int).
Remove uses of max() function (not available on some platforms.
Change I2C addresses from uint8_t to I2CAddress, in preparation for MUX support. Currently, by default, I2CAddress is typedef'd to uint8_t.
MUX support implemented for AVR and Wire versions.
Filter drivers provide extra functionality above a hardware driver. For example, a hardware driver for a PWM module may just set the PWM ratio, but a separate filter driver could animate motors or servos over time, calling the PWM driver to output the pulses. This would allow the animations to be easily implemented on a different type of PWM module.
Following on from the change to I2CManager_SAMD.h, the capability of deferring a request to change the speed of the I2C has been removed from the SAMD driver and put into the common NonBlocking code, so that all native drivers benefit from it.
To support nested drivers efficiently (i.e. to allow the higher driver to call another driver directly, without searching for a VPIN every time), the visibility of the IODevice::findDevice() function has been changed from private to protected.
The speed change is deferred until the next transmission is about to start to avoid issues with the I2C module being disabled and enabled during a transmission.
