Fixes #5079: Add API to manage Techniques

http://www.rudder-project.org/redmine/issues/5079
sys.path defines where python looks for dependencies

The first value 0, is by default the path where the script is ran

Here it adds ncf_tool_dir and DEFAULT_NCF_DIR so we can access to ncf module

In fact some lines are useles hees... and I should only add /usr/share/ncf/tools