EGIAmpServer with native sampling rates and support for TTL triggers

• Turns off anti-alias filter to achieve native sampling rates.
• Adds a digital input channel to the stream, which represents the binary state of the 16 digital inputs as a 16-bit integer cast to Float32 and sampled at the same rate as the EEG.
• Drops support for amps that don't use packet format 2 (i.e. 300 amps or 400+ amps with out-of-date firmware).