reorg for GIE and its v2 code.

[yecol]

Currently, the organization of the files:

├── src
│   ├── api
│   ├── assembly
│   ├── common
│   ├── coordinator
│   ├── data_load_tools
│   ├── executor
│   ├── frontend
│   ├── instance-manager
│   ├── pom.xml
│   └── v2
│       ├── pom.xml
│       └── src
│           ├── main/java/com/alibaba/maxgraph/v2/
|               ├── MaxGraph.java
|               ├── MaxNode.java
|               ├── common               
|               ├── coordinator          
|               ├── frontend             
|               ├── grafting
|               ├── ingestor
|               ├── sdk
|               ├── store
|               └── tools

Suggestions:

• Since the v2 and v1(MaxGraph) would co-exist for a period, it would be better to organize them as a whole. Is that possible to move folders in v2 to the root, and merge the duplications (e.g., common, frontend, coordinator...)?

Sorry, maybe I misunderstood.

• v2: store(v2), it more suitable to move to root.

[yecol]

duplicated to #816