when returning list of outdated files provide more detailed information
when using Save with tooling do not use Metadata retrieve

also, when updating session data retrieve LastModifiedDate of all files, not just one, as
it seems that with tooling save of multiple files is not down in a single atomic transaction
NOT working version of async conflict check
fix bug - SimpleDateFormat initialisation as instance variable does not work for multi threaded cases
when not using Metadata retrieve(), load LastModified data of different XML Types asynchronously and in parallel
minor cleanup

removed redundant comments, added some more comments