Calculate a 'regulated' signal strength reading

[wilsonpage]

Currently we're regulating an calculating signal strength -> distance on the client in JS. This is bad as it means we have to send many events over the bridge every second.

If this work was done in native code then we would only need to send data over when the value changes. Bridge traffic is minimised and clients can stay dumb.

Signal strength varies dramatically and is largely inaccurate. Therefore readings should be buffered and rounded up/down to normalize these irregularities.