Add an enum lookup capability

[Fleker]

Translate from an enum, which may come from a register, to the enum value.

For example, see ADS1015. Programmable gain is a 3-bit field, while each combination relates to a higher-level value.

[Fleker]

Tasks for this:

• Create a '#/fields/' getter
• Add a when to do a dict lookup based on value from variable for

- programmableGain: '#/fields/ProgrammableGain'
- programmableGain:
  when:
    for: programmableGain
    0b000: 6144
    0b001: 4096
    0b010: 2048
    0b011: 1024
    0b100: 512
    0b101: 256