rpl: initial import of an attacker

[BytesGalore]

Rationale:
This RP introduces the possibility to attack RPL.
Right now it is possible to perform a rank-attack pretending to have a deliberately low rank.
Doing so will attract neighbour nodes to choose the Attacker as prefered parent, causing a partition of the topology.
This attack can easily affect a very large number of nodes.

Attacking can be triggered using shell commands.
edit: use the gnrc_networking example, and
just type rpl atk help in the shell to see how to perform basic attacks.

This RP is not meant to be merged to RPL and will remain WIP, but I think its probably useful for testing.

And now have fun :).

edit: (A version number attack is on the way) added.

[BytesGalore]

added DODAG version number attack, which allows an attacker to rise the DODAG version number.
The new DODAG version be will eventually distributed in DIOs by the Attacker affecting all nodes in the DODAG.

[cgundogan]

this sounds interesting. I would actually like it if you could move most of the code into a subfolder of RPL and then declare it as a module. This way your changes will be in different files and therefore we will have less merge conflicts (: You could do it in the same fashion I did for P2P-RPL

[BytesGalore]

@cgundogan sounds like a good idea, I will try to out-source the source :)

[kYc0o]

Feature freeze -> postponed.

[miri64]

Postponed due to Feature Freeze.

[OlegHahm]

@BytesGalore, what's up with this PR?

[BytesGalore]

@OlegHahm I close this one, since I'm the only one using the features.
I will maintain this branch in my fork.