v4.2

I modified some parts to allow the use of large-scale models and large datasets.
For example, I replaced some 32-bit integers with 64-bit integers.

v4.1

• This new version supports difference filter.
• The error calculation of log10(apparent resistivity) is modified.
• Rotation angles of distortion matrix are limited to from -90 to 90 (deg.) when gains and rotations of galvanic distortion are estimated from this version.