* Renamed a couple more chain => core
* Updated VM `pc` to be uint64 rather than big int
* XEth interface cleanup

This moves call and create to the specified environments. Vms are no
longer re-used. Vm uses environment's Call(Code) and Create in order to
execute new contracts or transfer value between accounts.

State transition now uses the same mechanism described above.

Fix for broken develop build and install.sh