Builds on #11772, #11773 and #11817. Please review those PRs first.

Final step in #10603.

- First commit removes bip9-softforks.py.  bip9-sofforks.py was intended to be a generic test for versionbits deployments. However, it only tests CSV activation and was not updated to test segwit activation. CSV activation is tested by bip68-112-113-p2p.py, so this test is duplicated effort. Rather than try to update it to use the BitcoinTestFramework, just remove it. (see https://github.com/btcdrak/bitcoin/pull/8 for previous discussion around the redundancy of bip9-softforks.py)
- Second commit removes the now unused BitcoinComparisonFramework class and the comptool and blockstore modules.