Use NTTEC for erasure coding

[slaperche-scality]

Quadiron should be able to use NTTEC to split a file into chunks and distribute them to the nodes.
It should also be able to retrieve the chunks to rebuild the original file.

What we need is:

• to have an erasure coding module, that relies on NTTEC
• to have two new method (for now in the simulator shell, later in the RPC interface):
  • "put filename" (when using REST we will give the data directly instead of the filepath): read the file, apply erasure coding on it and store the chunks.
  • "get KEY": retrieve the data identified by KEY (find the chunks, fetch them and rebuild the file, send back the file to the user).

We should also be able to retrieve the file, even if some parts are missing (that's the reason for erasure coding after all).