Refactor Servos tab

[rotorflight]

The servo configuration has been totally refactored in the firmware. The parameters are reflecting the internal function of the firmware, and should not be exposed to the end-user directly. Instead, the Servo tab should offer more user-oriented view for the configuration.

The best idea so far is to have the following parameters offered for each servo:

• Servo type: 1520us or 760us or custom
  • Custom can't be selected by the user. It is selected if the current servo configuration in the firmware is neither 1520 nor 760.
  • If custom is active, all other fields are disabled
• Center (arm levelling) trim: -20.0% .. 20.0% (trim for correcting the center position)
• Max/Up trim: -20.0%..20.0% (trim for correcting the up position)
• Min/Down trim: -20.0%..20.0% (trim for correcting the down position)
• Max/Up travel: 50.0%..150.0%. (maximum is up direction when mounted on the heli)
  • 100% is equivalent to 50deg movement
• Min/Down travel: 50.0%..150.0% (minimum is down direction when mounted on the heli)
• Update rate: 50Hz..480Hz (1520us) or 50Hz..960Hz (760us)
• Servo reverse toggle
• Geometry Correction toggle (for rotational servos)

Let's also move the "Enable Servo Override" to the Servos tab.

[egonl]

I don't like the idea of imposing limitations to what the user can specify in the Configurator. I think it should only give warnings when values are unusual.

[rotorflight]

Job done.