Skeleton branch: main data structures and functions.
The struct node's marking now has zero length.  Implement marking copy.
Implement node_create, node_destroy and node_root.
some basic functions done
File handling part written
read_net / write_net working
added accel
main function working , but code as of now is very untidy : print function not working
Makefile working ok
New header file for list_nodes
2 more examples
some changes
Simplify a bit the makefile.
Cleanup.
Revert "dummy commit" to simplify upcoming merge.

This reverts commit 2d90e7d7ad22a1152b11ed8cd1c8747182e9bf91.
Merge branch 'skel'