OrientDB 2.1-rc1 发布文档数据库

OrientDB 2.1-rc1 发布，此版本解决了 104 个 issues，主要更新内容如下：

Schema:
- Support for Multiple inheritance where classes can extend from multiple super classes
- Support for default values (functions are allowed)
Core:
- Improved WAL management (Journal) to enforce Consistency with transactions
- Fetch-plan supports wildcard for names
SQL:
- New SQL parser by default on with new databases and off with those created with old versions
- Prepared Statements and substitution of parameters and target
- New Live Query to write Reactive applications
- New optimization about using of indexes in sub-classes if present
- New concat() function
Distributed:
- Support for slave (read-only) nodes
- Included Hazelcast-all.jar including also Cloud support
ETL:
- Skip duplicated vertices
Bug fixing: 104 issues in total