Commands Refactor Part 2

We split #196 in two parts. this is the second. (#262 is the first). This builds on all the changes to commands/.
Wait, why are you changing help text? don't do this in this PR. This should be:

```
ipfs block is a plumbing command used to manipulate raw ipfs blocks.
Reads from stdin or writes to stdout, and <key> is a base58 encoded
multihash.
```