Basic support for lists in config.yaml

[nils]

DRAFT
This is just a FYI PR in case anyone is interested in what I'm doing.
No expectations from my side attached to it at the moment (no expectation to have it merged, reviewed, ...)

Initial work on allowing YAML lists to instantiate multiple objects of the same type (see #341 for a use case).

There are many things that need to be improved or that are missing at this point. (also see @MitchBradley's comments on #341)

Currently it allows me to do what I had in mind (but not much more, I assume):

[ ... ]
besc:
  - pwm_hz: 50
    output_pin: gpio.12
    enable_pin: gpio.13:low
    direction_pin: NO_PIN
    disable_with_s0: false
    s0_with_disable: true
    spinup_ms: 0
    spindown_ms: 0
    tool_num: 0
    speed_map: 0=0.000% 255=100.000%
    min_pulse_us: 500
    max_pulse_us: 2500

  - pwm_hz: 50
    output_pin: gpio.33
    enable_pin: gpio.27:low
    direction_pin: NO_PIN
    disable_with_s0: false
    s0_with_disable: true
    spinup_ms: 0
    spindown_ms: 0
    tool_num: 100
    speed_map: 0=0.000% 255=100.000%
    min_pulse_us: 500
    max_pulse_us: 2500

Next steps:

• Think about how to implement enterSectionList on the other HandlerBase subclasses.
  • i.e. addressing scheme proposal (RuntimeSetting?), e.g. $besc/0/pwm_hz
• potential future extension: reference other items from another branch of the tree (to e.g. define motors globally, only reference them from kinematics)

[nils]

Looks a bit fishy. I could introduce another member on Token as well, but it would basically do the same, I assume.

[nils]

Had to make BuilderBase a non-inner class to be able to forward declare it in HandlerBase.h

[nils]

Reason: It could also be a plain scalar (e.g. -42)
But did this YAML parser support that before? I guess not, it always relied on "key: value" pairs.