Support for setting Postgresql DB schema via configuration

Currently Hive services support the following Postgresql connection properties:
```
| `POSTGRES_SSL` | No | Whether the postgres connection should be established via SSL. | `1` (enabled) or `0` (disabled) |
| `POSTGRES_HOST` | **Yes** | Host of the postgres database | `127.0.0.1` |
| `POSTGRES_PORT` | **Yes** | Port of the postgres database | `5432` |
| `POSTGRES_DB` | **Yes** | Name of the postgres database. | `registry` |
| `POSTGRES_USER` | **Yes** | User name for accessing the postgres database. | `postgres` |
| `POSTGRES_PASSWORD` | **Yes** | Password for accessing the postgres database. | `postgres` |

```
It would be beneficial to have yet another property allowing to set custom Postgresql schema for the connection (similar to `currentSchema` in JDBC connection string or `SET search_path TO ...`)