SLING-3074 : introduced SerializationDataBuilder - which you get from the factory-method SerializationManager.newBuilder() - and you're supposed to destroy() it, once done. This refactoring allows to reuse the vault's filesystem object and speed-up import substantially

git-svn-id: https://svn.apache.org/repos/asf/sling/branches/tooling-ide-vlt@1524434 13f79535-47bb-0310-9956-ffa450edef68