Add freezer migrate

[Tristan-Wilson]

This adds the geth binary to the nitro-node image, so that the "geth db freezer-migrate" tool can be used, to fix issue #1745

Adding geth adds about 54MB uncompressed to the nitro-node image.

Testing done

Checked that geth with the db freezer-migrate tool is present.

$ docker build --target nitro-node -t nitro-node .            
 ---> 3064ef4251f4
Successfully built 3064ef4251f4
Successfully tagged nitro-node:latest
$ docker run -it --entrypoint /bin/bash 3064ef4251f4
user@6ef1bbaf05ac:~$ /usr/local/bin/geth db freezer-migrate
INFO [07-27|00:08:31.021] Maximum peer count                       ETH=50 LES=0 total=50
INFO [07-27|00:08:31.022] Smartcard socket not found, disabling    err="stat /run/pcscd/pcscd.comm: no such file or directory"
INFO [07-27|00:08:31.023] Set global gas cap                       cap=50,000,000
INFO [07-27|00:08:31.023] Using leveldb as the backing database 
INFO [07-27|00:08:31.023] Allocated cache and file handles         database=/home/user/.ethereum/geth cache=512.00MiB handles=536,870,908
                                          

[Tristan-Wilson]

Closing in favor of OffchainLabs/go-ethereum#245