Refactoring Commands

Now that we have the `commands` package set up, it's time to move everything over to it. This PR is currently not ready for merge, just setting it up for CR.

The basic scope of this PR is as follows:
* Set up transports based on `commands` package (HTTP RPC server/client, CLI command handling)
* Refactor existing commands for the new API (won't be a 1:1 mapping, commands will change)
* Make changes to `commands` package when necessary
Readme missing current state:

```
ipfs - global versioned p2p merkledag file system

Basic commands:

    init          Initialize ipfs local configuration.
    add <path>    Add an object to ipfs.
    cat <ref>     Show ipfs object data.
    ls <ref>      List links from an object.
    refs <ref>    List link hashes from an object.

Tool commands:

    config        Manage configuration.
    update        Download and apply go-ipfs updates.
    version       Show ipfs version information.
    commands      List all available commands.

Advanced Commands:

    mount         Mount an ipfs read-only mountpoint.
    serve         Serve an interface to ipfs.
    net-diag      Print network diagnostic

Plumbing commands:

    block         Interact with raw blocks in the datastore
    object        Interact with raw dag nodes


Use "ipfs help <command>" for more information about a command.
```