Rename ArcLengthParameterization module to ArcLength

[ianmackenzie]

Should still be very unlikely to result in a naming conflict, and would have a couple of advantages:

• Would allow for some shorter function names:
  • ArcLength.parameterization instead of ArcLengthParameterization.build
  • ArcLength.toParameterValue and ArcLength.fromParameterValue instead of ArcLengthParameterization.arcLengthToParameterValue and ArcLengthParameterization.parameterValueToArcLength
• Would allow for arc length calculations that do not involve building a parameterization, such as ArcLength.estimate (same arguments as ArcLength.parameterization, but just returns a total arc length estimate without actually building up a parameterization data structure)

Could potentially add an ArcLength module now, and have the ArcLengthParameterization module basically be a deprecated alias for it until the next major version...