SensorRelay fixes

[nekromant]

This MR attempts to fix the problem of relays toggling on/off during initialisation, especially active-low relays. This can be a big problem if a board has some 8 relays toggling some serious loads.

[nekromant]

@user2684 There seems to be some CI problem that's definetely NOT related to this MR

 ls -l --recursive ./examples/RFM69/build/
ls: cannot access './examples/RFM69/build/': No such file or directory

[user2684]

@nekromant Hi, sorry for reviewing this soooo late! A couple of random comments:

• Yes, the checks failed are not due to your code, this is something I will need to fix in a different PR
• I see you call setStatus() before initializing the pin with pinMode(). Are you sure this is not creating issues?
• The "inverted" variable in SensorRelay. would you please add it as the last parameter of the class? Otherwise would break compatibility with other sensors inheriting from it
• Can you please add newly added functions to README.md?

Thanks a lot!

[nekromant]

I see you call setStatus() before initializing the pin with pinMode(). Are you sure this is not creating issues?

Precisely! The spurious relay click happens between the moment we set the pin mode to output, and before we write the actual value to the pin. This way we have a value we want to use in the actual register before we change modes, thus avoiding the glitch.
As a side effect, on avr this enables/disables the pull-up, but that should match the desired pin state later on.

As for the rest, I'll fix it ASAP.

[user2684]

Interesting, thanks, never had the chance to notice it!