RangedFloat cleanup
* Add Min / Max properties instead of x / y fields, fields are obsoleted
* Max always equals Min for Fixed range type, unlike the old y field
* ToString returns "<min>" for fixed values, or "<min> <max>" for ranges, instead of "<min>,<max>,<type>"
* Parse supports old format
* Can deconstruct: `var (min, max) = range;`
* Add tests parsing old format