Enable High Power and Voltage Limit

[swissfreek]

This enables high power via auto detection of tip resistance (1.5-2.5ohm for RTM, 3-4ohm for RTU, otherwise UNKNOWN).

It dynamically adjusts output power as it runs based on the determined tip resistance. For RTM tips, it allows a max of 40W. For RTU tips, it currently only allows a max of 15W, until testing can validate that the code works properly, and then max power will be increased to the full 150W.

It limits power to 150mW in case the tip is UNKNOWN in order to prevent damage. This is set every time the _start() cycle runs so that switching from RTU to RTM does not cause damage.

It adjusts the scale of the power display bar for 40W or 150W output.

It also forces a stop and displays an error on the display if voltage is more than 14V when an RTM tip is plugged in, or 25V when an RTU tip is plugged in.

Sorry I'm creating a new pull request, I couldn't figure out how to change the code when I found errors before, so I started over.

[swissfreek]

One thing I have noticed is that the additions to the code definitely have an impact on the PID loop, and the controller now appears to be over damped. It doesn't overshoot a few degrees like it used to, and doesn't reach the set temperature, but instead settles about 3ºC too low. I doubt constantly setting the PID constants would cause that since they're... constant. But maybe the extra processing time that the new code adds slows the response time just enough that the PIDs are a little off? Not even sure if that makes sense. I should be smarter on this stuff since I went to school for it, but sadly it has been a while and I'm not.

Ultimately, I'm not sure that settling 3 degrees low is a very big deal, but I haven't been able to put a real thermal load on the tip to test and see if there's a more significant effect while working. So far I'm just looking at the idle behavior. But it looks possible that these new features may also require slightly tweaked PIDs, even for the RTM tips.