Add K6517B as voltage source

[arnobaer]

Note: for IV measurements, when selecting only ELM instrument, the ELM acts as voltage source (if the instrument supports it).

Implement following methods for K6517B drivers:

• get_output_enabled() -> bool
• set_output_enabled(enabled: bool) -> None
• get_voltage_level() -> float
• set_voltage_level(level: float) -> None
• set_voltage_range(level: float) -> None
• set_current_compliance_level(level: float) -> None
• compliance_tripped() -> bool