Improve handling of big deposits

[jonasraoni]

The Preservation Network has a hard limit regarding the deposit size, which is currently 1GB, given that some deposits exceed the current 1GB threshold, it makes sense to find a solution to accommodate them.

Solution
Adding support for depositing individual submissions sounds like a good solution. It should substantially decrease the size of deposits, while also making room for the preservation of preprints and continuous publications.
The issue/volume number and the publication order within the issue can be attached as metadata.

Other improvements/ideas

• Update the native plugin to upload only the latest revision of the submission
• Allow the user to setup rules (e.g. ignore video files, files bigger than X, remove biggest files until it fits, etc), which might be applied when the deposit exceeds the limit
• Allow the user to manually select which files/submissions he wants to skip
• Breaking the package in pieces is probably not doable (if it is, it will require some research)