[ISSUE #262]Dledger polish project

[mxsm]

tracing #262

• Optimize module structure, add a common module

[RongtongJin]

Whether it is necessary to extract the common module separately because the core and the common module are used together now

[RongtongJin]

To ensure compatibility, it would be better not to modify the artifactId.

[mxsm]

Whether it is necessary to extract the common module separately because the core and the common module are used together now

command module is noly for CLI , it can't start dledger server. Multi-Raft start with proxy module and normal start with dledger module. so add common module