Special handling for attachment archiving for T&Q and user files

There are 2 cases where references to attachment files archived in attachment.xml do not match between what’s archived by the tool, and the ids in attachment.xml

1. Tests & Quizzes: the QTI archiving code removes spaces from attachment paths for unclear reasons here: perhaps spaces in paths may not be supported in that version of the QTI spec

2. References to files in user workspaces (e.g. in HTML content) have the form /access/content/user/EID/somefile whereas they are archived with /access/content/user/ID/somefile. These may not be possible to resolve correctly if the user concerned is not part of the site being archived (otherwise it would require a full archive of the entire user base to map EID to ID).

To allow the archives to be internally consistent, the cleanest solution here is to change the paths of the resource ids in attachment.xml to match how they are referenced from tool archive files. This needs to be done in BaseContentService, which seems like it shouldn’t need to be concerned with this detail, but there doesn’t appear to be a cleaner solution without much larger code changes.