This allows to reuse it across different packages.
testchain can't be used because of circular dependencies.
Init() is not changed except for filepath.Join() use instead of direct string
appends which is a better approach anyway. rootpath is required because
current directory will change from package to package.
We need to store NEO balance's LastUpdateHeight before GAS mint,
because mint can call onNEP17Payment and onNEP17Payment can call NEO
transfer which also calls GAS mint. Storing balance height allows to
avoid recursion.
If a method is known at compile time we can still check
if it is present in the list of methods of at least one contract.
Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>
