LIVEOAK-678: fixed column add/delete issues
Merge pull request #396 from vrockai/LIVEOAK-678

LIVEOAK-678: fixed column add/delete issues
Refactor ConfigResource to be MappingResource, as it's purpose is more general than just mapping from config
LIVEOAK-684 ExtensionInstaller uses cached ConfigurationManager when no config file defined
- Add some tests for verifying system extensions
- Move system extension classes into extension package
LIVEOAK-681 Resource extension type always returns "null"
- Removed some items from ConfigurationManager that were more appropriate on the wrapping resource
- Added methods on wrapping resource to handle differences between application and system extensions for retrieving versioning information and extension id