ENH: Merge cvMesh functionality into cv2DMesh

- Added conformationSurface and searchableSurface classes in place
  of querySurface.
- Added cellSizeControl class.
- Change cvMesh argument of relaxation model constructor to Time.
- Add writePrecision option to surfaceConvert.
- Add onLine function to surfaceFeatureExtract.
- Remove querySurface.
- Move createShellMesh and extrude2DMesh to their own libraries.
- Replace controls and tolerances with a cv2DControls object.
- Add patchToPoly2DMesh class to extrude2DMesh.