Ert 791 write restart file wellinfo

Prepared ERT code to write well info to restart files. This functionality will be used from OPM, and it is tested from OPM code ( opm-core, unittest "test_writenumwells"). The written restart files will contain enough information to be opened successfully in Resinsight. The well trajectories can be viewed for each timestep in Resinsight. 
The restart files written does not contain enough information to be read by ECLIPSE, this will most probably crash and burn.