4.3.0.8 Release candidate 2

This is the most up to date candidate for 4.3 branch, post fork.

4.3.0 was a mandatory update, in order to support the fork at block 1 200 000.
See: https://hypernodes.bismuth.live/?p=586

This release brings cleanup and safeties for late upgrades, or post-fork upgrade.
It's also the required release for newest hypernode versions, beta99 branch.

Warning: if upgrading from a previous version:
From the Bismuth directory, do:

• pip3 install bisbasic
• pip3 install -r requirements.txt
• rm -rd polysign