In Memory File Zipping

[jachaos]

Replace the code to zip the files in memory instead of writing them to
the disk first and some minor code adjustment and cleanup.

I was working on this code to submit files through the IDES Gateway, when creating several files or the same file multiples times it becomes bit messy having all these files in the destination folder, generating just the final zip file without the need of creating the "temporary" files first would produce a cleaner result. And the user can always find the files inside the .Zip file in case he wants to take a look to them.

Also moved the Creation of the Metadata XML file to the XMLManager class.

[MrGeneric]

Much more elegant than my solution of programatically deleting the leftover files, nice work. Would be nice to see this merged.