added new unit test to opm-core to test if number of well are read and written to the reset file

Created unit test and added to cmake

Test commit

Added testdata to cmake file
ERT-791: Added numwells, needed as argument to ecl_rst_file_fwrite_header()
ERT-791: Added RUNSPEC and GRID to test DATA file
ERT-791: Write number of wells in restart file header
ERT-791: Testing that written number of wells written to restart file equals number of wells read from schedule file
OPM-139
OPM 139
OPM-139
OPM-139
OPM-139
OPM-139
OPM-139
OPM-139