Bangle.getPressure() redesign

[d3nd3]

Fixes #2445

I decided to keep the timeout as the comments suggest there need to be a minimum delay after turning on. But still utilized the code in the periPollHandler to resolve the promise.

[d3nd3]

You have a choice whether a Bangle.on("pressure") callback fires from a Bangle.getPressure(), currently it does.

[d3nd3]

Okay. I am fairly happy with the code.

• When Bangle.setBarometerPower(1) is set prior to using Bangle.getPressure(), it has fast response as described in the docs, albeit the value isn't 'fresh' necessarily, as expected.
• If user uses streaming Bangle.on("pressure'), he gets 'fresh' values, they come as fast as they can whilst being fresh.
• Decide if you like it that Bangle.on("pressure") triggers during the temporary activation during Bangle.getPressure().

Feedback welcome.

[gfwilliams]

Thanks - I'll post some comments in the issue...