Package Errors:
- add function to check & cast error interface into golib Error interface
- update CodeError type to simplify management & error creation
- add function to simplify call of Error function from a generic error interface
- remove some useless function from Error interface
All Other Packages:
- apply change of package Errors into all other packages
- based on dragonboat lib (https://github.com/lni/dragonboat)
- add extended config with validate
- add backend managment to allow simple implementation for backend simple, cocurrent & disk
- has no backend implemented and must be a lib for a cluster mode of one backend
