Mmgen-wallet

**Data directory, config file and default wallet support**
- Data directory is `~/.mmgen`; config file is `mmgen.cfg`.
- When default wallet is present in data directory, specifying the wallet
on the command line is optional.
- Datadir structure mirrors that of Bitcoin Core: mainnet and testnet share
a common config file, with testnet putting its own files, including the
default wallet, in the subdirectory 'testnet3'.
- Global vars are now overriden in this order:
1) config file,
2) environmental variables beginning with `MMGEN_` (listed in 'globalvars.py'), and
3) command line
- Long (common) opts added for setting global vars; display with `--longhelp`.

The test suite has been updated to test these new features.

**Other changes**
- Always get user entropy, even for non-critical randomness, unless `-r0`.
- rpcuser,rpcpassword now override cookie authentication, as with Core.
- Communication with remote bitcoind supported with `--rpc-host` option.
- Testnet use can be overridden with the `--testnet=0|1` option.

**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

**New features/improvements**
- Address generation using secp256k1 library (Linux only)

Instructions for installing the secp256k1 library on your system can be found at 'doc/wiki/install-linux/Install-MMGen-on-Debian-or-Ubuntu-Linux.md'

If secp256k1 is not installed on the system, MMGen will still be usable. It just falls back to 'keyconv', or failing that, python-ecdsa for generating addresses.

- Windows support updated
- Colored output

![mmgen-txcreate running in a terminal window]

New features/improvements:

* New native Bitcoin RPC library.
* Support for cookie-based RPC authentication (new in Bitcoin Core v0.12.0).
* Batch mode available when listing and importing addresses.
* mmgen-tool listaddresses: 'addrs' argument allows you to specify an
address or range of addresses.

NOTE: if MMGen is already installed on your system, you must remove your
existing installation by hand before installing this new version. On Linux,
this means deleting everything under the directory
'/usr/local/lib/python2.7/dist-packages/mmgen/'. Also, if you did a 'git pull'
instead of a fresh clone, you must delete the 'build' directory in the
repository root before installing.

The 'mmgen-pywallet' utility has been removed. It's no longer needed, as the
'bitcoin-cli dumpwallet' command (available since Core v0.9.0) provides
equivalent functionality.

The Windows port isn't being actively maintained at the moment. Use at your own
risk, and report any problems on the Bitcointalk forum.