Fix the cylinder pressures in the CSV summary export. Only show
pressures derived from `pressure` attributes in samples for the first
cylinder. Add support for showing pressures derived from `pressure0` ...
`pressureX` attributes.
Also cleaned up unit conversions, and changed tabs to spaces.
From discussion in
https://github.com/subsurface/subsurface/pull/3906#issuecomment-1575980882.
Signed-off-by: Michael Keller <github@ike.ch>