Block cipher operation modes: ECB, CBC, CTR and CCM

Hey.

This is the followup to #1200. Refactored, rebased and without the crypto shell example. It adds support for ECB, CBC, CTR and CCM (RFC 3610) block cipher operation modes. This is the version we are currently using in our DTLS working branch. To omit a pull request of death for DTLS we would be happy if we could manage to merge this before.

Regards
Nico
Well that's ok for me but I addressed this issue with https://github.com/RIOT-OS/RIOT/pull/1342#issuecomment-49778490 - 22. July: 

```
You might wonder why are there so many code additions/deletions. It seems the existing cipher implementions did not follow the coding conventions of RIOT (.astylerc). As we structured the crypto part (moving files into new dirs) and fixed the coding style we ended up just for this with 2,870 additions and 2,880 deletions. (see 41695d0 - if thats not in your mind I can remove this commit from the PR).
```

As you can see I talked about these concerns and offered to remove this commit five months ago.