core/commands: Don't use pointers for Type field

core/commands: Refactored command marshalers

I made the commands lib dir listing sort the contents
so we get the same sequence of files from it repeatably.

sharness test: ipfs add -r

License: MIT
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>

License: MIT
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>

May not be necessary to sort when adding each link--
doing so would be unnecessarily expensive O(n^2) when
constructing nodes -- though n wont be big.

Implement recursive indirect block creation for DAGs

improve efficiency of multilayered indirect blocks

clean up tests

panic cleanup

clean up logic, improve readability

add final root node to the dagservice upon creation

importer: simplified dag generation

test: updated hashes using latest code

@whyrusleeping this is why the sharness tests
were failing: the hashes are added manually to
make sure our generation doesn't change.

cleanup after CR

fix merkledag tests

fix small block generation (no subblocks!)

blockservice async exchange.HasBlock

bootstrap add --default option

this commit:
* moves parsing of bootstrap peers into config
* moves location of bootstrap addrs into core/commands
* refactor `*BootstrapPeer -> BootstrapPeer

sharness bootstrap rm

if a test is cancelled, unmount may not run. then, must
run umount before mounting, just to make sure.

sharness tests should not bootstrap to the dht. it
may be useful to test that specifically, but not on
the other tests.

feat(dht) Bootstrap

use dht bootstrap. there is an edge case where the dht
is tiny (1?) and we have 0 bootstrap peers. we should
probably _inform_ the user, but this may be more a
webui or command thing.

This also makes it an Error to find a peer.