Add color codes for enum telemetry

[timcanham]

For FPP, an enumeration looks like this:

enum Decision { YES, NO, MAYBE }

Telemetry already has a notion of color codes for scalars:

@ Telemetry channel 1
  telemetry Channel1: U32 \
    low { red 0, orange 1, yellow 2 }

There are cases where it would be very useful to color-highlight enumeration values in telemetry in the ground system.

For example:

enum AlarmLevel {NOMINAL, WARNING, CRITICAL}

An update to the telemetry channel definition to accommodate this could look like:

@ Alarm telemetry
  telemetry HeaterAlarm:  AlarmLevel \
    color { orange WARNING, red CRITICAL }

enumeration values not specified would have the default color.

There is currently no support in the XML for this.