*Assorted fixes/improvements*

- Importing addresses with `--rescan` working again
- Tracking and spending non-MMGen addresses now fully functional
- `mmgen-txcreate`: improvements in unspent outputs display
- `mmgen-txsign`: use bitcoind wallet dump as keylist fixed

- Testnet support:
  - Practice sending transactions without risking funds
	(free testnet coins: https://tpfaucet.appspot.com/)
  - Test suite fully supported
  - To enable, set `MMGEN_TESTNET` environment variable