Helps seeing where the cursor is when displaying data over previous screen

![image](https://user-images.githubusercontent.com/6101998/134028533-5f190252-ad71-43c5-accc-c2b7b6c49663.png)

Signed-off-by: k <k@klabz.org>

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

This one picked up a lot of inconsistancy so the changes here are pretty
big.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

By default bright and mid are white/grey tones, the ui widgets are
blue and the spot colours are different variants of orange.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

The algorithm is fairly crude and the GUI is pretty simple but, if you stay
still for 10 seconds, there's a good chance of an accurate pulse
reading.

Of course if you jog on the spot for ten seconds it more likely to
calculate how many steps per minutes you are performing!

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>

The heart rate analysis step is still a work in progress but the current
app allows us to visualize the the results of the signal conditioning.

Signed-off-by: Daniel Thompson <daniel@redfelineninja.org.uk>