This commit fixes the module-level docstrings for the tests and helper
modules in qa. Many of these tests were uncommented previously - this
commit ensures that every test case has at least a minimum level of
commenting.
mininode now supports witness transactions/blocks, blocktools
has a helper for adding witness commitments to blocks, and script
has a function to calculate hashes for signature under sigversion
1, used by segwit.
Py3 conversion by Marco Falke
Test to make sure upgraded nodes don't ask for non-wit blocks by
Gregory Sanders.
