- ReadConfig initialiser sets up global ethutil.Config via config file passed from wrappers
- does not write out adhoc default (not meant to) but creates empty config file if it does not exist so that globalconf does not complain if persists a flag
- default datadir and default config file set together with other flag defaults in wrappers
- default assetpath set together with other command line flags defaults in gui wrapper (not in ethutil.Config or ui/ui_lib)
- add EnvPrefix, to handle environment variable options too via globalconf
- this is still transitional: global Config should just be a wrapper around globalconfig config handler and should be moved to go-ethereum
- actual eth stack config should not be global instead config handled properly with explicit dependency injectioninto eth stack component instances