Use urls for uploads in the store and file browser

Merged David Sikter requested to merge 828-use-upload-urls-in-store-and-file-browser into develop

A part of the refactoring for #828 (closed). The store is updated to use installationUrl + uploadId, rather than just uploadId to manage uploads, and the file browser adaptors are updated so they take absolute upload urls as the main argument (containing information about installationUrl + uploadId + rawPath), rather than just uploadId + rawPath. Some additional work still needs to be done before we can actually fetch data from external installations, though, so only urls pointing to the local installations work for now.

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