Resolves #4166
Resolves #4163

This PR tries to resolve two issues with QuantityType:

1. Updating a Number:Dimensionless Item with a value of unit one, when the unit is set in metadata to another unit, will not update correctly. The proposed solution is to remove the special handling of unit one and make the unit part of the string again. It can be removed from visualisation using a state description.
2. Formatting a QuantityType tries to use the DateTime String formatting methods. When it fails it may output a UTC date. Durations will also not be correctly formatted when days/hours/minutes/seconds are above the month (31)/day (24)/hour (60)/minute (60) limits. In this PR, the formatting strings are preserved, but interpreted specifically for time with a relative scale (durations), rather than an absolute time.