create new sysex-based implementation of ServoFirmata

[soundanalogous]

The existing use of the analog message to send the servo value does not work well in the decoupled configurable firmata architecture. ServoFirmata should switch to a sysex-based implementation that will eliminate the need for AnalogWrite.h. The pattern of using the analog message to send arbitrary values should no longer be used for ConfigurableFirmata.