Enchancements to v1.2

[ZiGaMi]

I'm looking at FOC shield v1.2 and have following proposal to address for the future revision:

1. Add DC-link voltage measurement (resistor divider + RC filter), as it is essentail for proper FOC,
2. Place thermistors (NTC) close to MOSFETs and/or DC-link capacitors. Knowing those temperatures is essential to prevent damage to inverter,
3. Current BOM has 35V DC-link capacitor and the board is specified up to 35V, thus having no reserve for DC-bias on those capcitors. I'll recommend to replace with at least 50V cap
4. Place more DC-link capacitors, more the better :D
5. Add some potenciometer