Scope reports by repository

Also show info message if there are no repositories available to a user (lost after redesign).

And move the "Reports" menu item from the "System" menu to the repository toolbar.

Re: report scoping...
So each report may need to apply the repo scope depending on the nature of the query.  The abstract report offers a generic "where" statement on the dataset and reports can override this.  Eg. the unprocessed accessions report has to override scope_by_repo_id to qualify this scope to the accession table.