Hpim-dm

Fix fragmentation of Sync messages when IPv6 is being used and fix a possible deadlock scenario

Fix removal of IGMP/MLD interfaces. Method for removing membership interfaces didn't have the correct arguments for dealing with these types of interfaces.

This version brings IPv6 support:
- Implementation of IPv6 multicast routing interaction with Linux kernel;
- Control packets have IPv4/IPv6 interpretation (field lengths) based on the type of interface that receives those packets;
- IPv6 HPIM interface;
- MLDv1 support;
- Interaction with IPv6 unicast routing table.

Fix exception in case log folders already exist

Add keywords to PyPi.org project

Include changes to prevent loops when a router has multiple interfaces directly connected to the source. This bug was detected around August of 2019 and fixed in this version.

Features to prevent this loop:
- non-root interfaces connected to the source don't forward any data packets;
- at the source subnet there are no upstream nor interest messages exchanged regardless of interface role (this allows state to be maintained consistently on all routers);
- Sync messages transmitted by interfaces directly connected to the source subnet of trees don't include those trees as part of the snapshot.

This version includes:
- Updated State Machine documentation;
- Updated code to prevent these loops