Added SQLite storage module.

Includes:
 * Base module for all SQLite backends
 * Backend implementation based on xerial SQLite driver
 * Implementations of object, graph, config, and staging storage
Enable sqlite as a storage backend option for CLI
Merge branch 'sqlite2' of github.com:jdeolive/GeoGit into jdeolive-sqlite2
set geogit-sqlite version to 0.8-SNAPSHOT