ERT-480: Added optional offset argument to point_fprintf().
ERT-480: Added tetrahedron_fprintf function.
ERT-480: Added NTG and MULTPV checks in grid volume checks.
ERT-480: Added method cell_regular.
ERT-480: Reformat slightly.
ERT-480: Added header for ecl_grid_regular1() functions.
ERT-480: Changed cell contains implementation to only consider simple planes for each cell.
ERT-480: Added assert.
ERT-480: Added assert_center before accessing cell depth.
ERT-480: Removed unused variables.
Merge pull request #407 from joakim-hove/ERT-480-submit

Ert 480 submit