Mount, Daemon, and Signal Handler Fixes

This is because if the user specifies that they want
to mount multiple times, something must be wrong. try
unmounting to reset things and then proceed.

This commit changes the signal handler to be added once
the command is executing. this is because the daemon
has its own signal handler, that must try to shut down
the node gracefully first. You know, just in case.

This commit adds a Mount abstraction (which is really just
a wrapped context closer). It makes sure to bind the mount
to the fate of the Node (i.e. close it if the node ends).
This fixes #350

add in a default file hash and cleaned up init function a bit

@maybebtc fixed it. cc @whyrusleeping

sorry everyone.

 windows mount  fix

miscellaneous fixes

License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>

vanilla:
    21.57 real        45.14 user         8.51 sys

short:
    14.40 real        31.13 user         5.56 sys

License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>

License: MIT
Signed-off-by: Brian Tiger Chow <brian@perfmode.com>

@jbenet

remove 'adapter' concept
instead, describe the component as the bitswap network

it's still an adapter, but it's just not necessary to describe it as
such

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

fixes #293

https://github.com/jbenet/go-ipfs/issues/293