Some of the other clients don't bother to store block numbers as
256-bit integers (64 bits or even 32 bit are enough).
The changes here are based on helpers introduced in eth_common
that try to abstract away all conversion steps in the code between
VM words and block numbers in variables in fields. Unfortunately,
this turn out to be more work than anticipated and I've postponed
finishing the refactoring for now (Block numbers are still 256 bit).
* Move and cleanup interpreter files - prepare for redesign of VM
* fix call comment aobut recursive dependencies
* memory: use a template again and avoid (?) a cstring-> string conversion
* Fix stack test regression
* Fix recursive dependency on logging_ops, test_vm_json compiles but regression :/
* Fix signextend regression
* Fix 3 signed test and sha3 test