bug fix in generetae which don't take into account pass args
remove pdb
update in network:
new methods:
-  Network._get_edges_typ : specify type on an edge
-  Network._get_grp : get group of nodes
-  Network._get_llink : get link and reverse link
-  rename Network creation metho to invisible (_)
simulnet :
- update to be compliant with Network
- update default json files
- update device.py consequently
simultraj :
links created from network class
Merge branch 'master' of github.com:pylayers/pylayers