Add Support for Clustering Disk Connectors

The disk connector can share access to its on-disk storage with other disk connectors, making it suitable for use in a cluster. However, the connector uses a JVM lock to control repository access, so concurrent access to the storage area from different JVMs could lead to inconsistent results.

In keeping with the spirit of the DBC, the existing locks could (optionally) be configured to also attempt to gain a read or write lock on a file. This way, the OS could help synchronize access between different JVMs in a cluster.