utils.bitcoin: Add self-tests using external dataset

This uncovers that not all invalid addresses are detected,
which is also a problem with python-bitcoinaddress-0.2.2.tar.gz
bitcoin.utils: Add command line interface for checking hashes
bitcoin.utils: Add the rest of testcase with valid hashes
utils.bitcoin: Fix pyflakes 'math' imported but unused
Remove vendor/bitcoinaddresses-0.2.2.tar.gz (issue #2867)

This should fail the tests to be fixed in subsequent commit
by switching to new utils/bitcoin.py