Started work on ecl_nnc_export
Minor nnc reshuffel
Removed nnc_index_list implementation.
Removed moot test ecl_nnc_amalgamated.
Commented out ecl_nnc_export test.
Added if (== NULL) guard.
Added simple nnc_info fprintf function.
Large change to nnc internalisation:

  - Removed nnc_index_list -> indices go straight to a int_vector without any sorting or the like.
  - Only one direction of the NNC connection is added.
  - Significicantly rewritten the test, instead based on explicit scanning of the EGRID file.
Activated (empty) test for nnc export.
Added size() function to nnc_vector.
Added nnc_info_get_total_size() to get the total number of nnc's handled by this nnc_info instance.
Added function ecl_grid_get_num_nnc() which gets the total number of nnc for a grid.
Started work on exporing nnc data for Resinsight.
Renamed xxx_get_index_list() -> xxx_get_grid_index_list().
Added nnc_index as property to nnc_vector type.
Added nnc compare function for sorting.
Added some code for testing nnc export.
Added function ecl_nnc_sort() to sort a list nnc connection items.
Minor sizeof bug.
Geometric export of nnc works for the simplest grid case.