Also implements transactional block persistence. Two issues
in the transaction processing code have been discovered that
might affect other usages such as the CALL instruction.
The main fix gets us past block 49000.
You may need to clean up your database.
This blindly changes logging to nim-chronicles - issues that ensue:
* keeps gas cost computation logs hidden behind flag
* unclear if logScope is practical - for example, since vm is split over
many files, topics get lost when using simple top-level per-module
topics
* when passing named object around, scope should incliude the name of
the object but this is caught neither by logScope nor by dynamicLogScope
