Added transaction creation/signing scripts

	modified:   MANIFEST
	new file:   mmgen-txcreate
	new file:   mmgen-txsign
	modified:   mmgen/__init__.py
	modified:   mmgen/bitcoin.py
	modified:   mmgen/config.py
	modified:   mmgen/license.py
	new file:   mmgen/tx.py
	modified:   mmgen/utils.py
	new file:   scripts/bitcoind-walletunlock.py
	modified:   setup.py
...and transaction sending

	new file:   mmgen-txsend