Several fixes and new features, most important:
* Cube() class
* A general get_randomline() method
* Grid() class
* Make a rectangular shoebox grid
* Get a randomline (sampling) along a 3D grid with property
* More robust support for binary GRDECL format
* Possible to input dual porosity models from Eclipse (EGRID, INIT, UNRST)
* Surfaces
* Added a class for Surfaces(), a collection of RegularSurface (etc) instances
* Generate surface from 3D grid
* Lazy load of RegularSurfaces (if ROFF/RMS binary) for fast scan of metadata
* Clipboard support in from_roxar() and to_roxar() methods
* fill(), fast infill of undefined values
* smooth(), median smoothing
* get_randomline() method (more general and flexible)
* Points/polygons
* Added copy() method
* Added snap to surface method (snap_surface)
* Several other methods related to xsections from polygons
* Well() class
* Get polygon and and improved fence from well trajectory
* Look up IJK indices in 3D grid from well path