[Pulse] Pulse Counter P003 enhancement

[TD-er]

See forum topic

N.B. I created this PR for the contributor in the forum.
Not yet looked at the code changes myself.

[TD-er]

@clumsy-stefan Since you're using the pulse counter too, can you also have a look at this PR, which contains code change from someone suggested via the forum?
I also merged in your recent changes for increasing the resolution to micros.

[clumsy-stefan]

Sure, I'll have a look at it. the only thing that worries me after a first quick look is, that quite a lot of work is done within the IRS handling (although mostly compares and no calculations), so this could work well for low impulse rates (like energy meters) but fail on high rates (like fan's).

I'll do a version later on and check with my test fan (which can go up to 12'500 RPM).

[TD-er]

That's why I asked you to test it :)

[clumsy-stefan]

Had it running overnight on a couple of nodes and just now did a few tests... It seems that it's running stable and it could read my fan up to ~10'000 RPM as well in RAISINg/FALLING mode as in LOW/HIGH mode (which gave rouhgly half the cycle time, as expected). So I guess it would be OK to merge this one in as it add's the possibility to measure LOW and HIGH pulses.

[TD-er]

Thanks for testing.