Account Tracker / Hill Lists / Meter Readings

Added support for setting the meter conversion factor as part of a rate change. This is mainly for gas meters, e.g. where your meter units change from ft3 to m3. Adding a rate change on the day your meter changes lets you use a different conversion factor for each unit.

If your meter uses a single counter/reading, the most recent reading is now displayed on the Meters screen. This is useful when submitting readings to your supplier.

Minor bug fixes.