Danny Hindson authored Dec 22, 2020 and Zhang, Chen committed May 05, 2021

The ParameterMap::diff method has been updated to take an extra
parameter representing a tolerance to be used when comparing double
values between two parameter maps
The overloaded == operator has been modified to call diff with a
zero tolerance to avoid duplicating code
CompareWorkspaces also updated to pass the value of CheckAllData
into diff so diff can stop after first change rather than going
through the whole map
The diff logic has also been speeded up to cope with larger parameter
maps now that diff constants stored (esp for GEM)
Various updates to doc test and system test files
Shorten UnitConversionParameters enum class name
Remove use of EMPTY_DBL() from ConvertUnits::getDetectorValues in
preparation for moving into ExperimentInfo class and also fix
RemoveSpectraTest unit test that relied on this