File Upload: Investigate and potentially disable JSP file upload caching.

[kcondon]

The generated/jsp directory caches files that have been uploaded but not yet saved. After saving it deletes them. However, there seems to be a lot of orphans in the cache that are not being removed.

This ticket is to investigate better ways of managing this behavior:
disable, make cache directory configurable

[bencomp]

We experience this too. Via a support ticket we (@ekoi and @kcondon) discussed using a symbolic link to at least prevent having lots of orphaned files in the application directory. This seems to work, but a configurable directory is better. In DVN 3.6.2 it wasn't clear to us that there would be a difference between the temporary directory (which is configurable using a JVM option) and the "arrivals area" in which uploaded but not yet saved files are cached. I guess the same holds for Dataverse 4?