[Issue #437] redesign the schema of metadata.

[bianhq]

Support the new features in pixels metadata:

1. user management and role-based authentication;
2. range-based table partitioning;
3. schema versioning;
4. path-granular catalog management.

Currently, only the RPCs for catalog management are fully implemented.
In addition, the metadata of tables and layouts are optimized.
I also fixed a bug in layout permission conversion and a bug in layout dao's update method.