Revert "add ability to impersonate users to admin area"

This reverts commit e8b2681cf34578d864b31ec86cdb53daf4ecced2.

Better done as larger overhaul of user system.
add support for legacy route to DOAJ XML schema
send DOAJ XML schema file as attachment, mimic nginx behaviour on the new route
fix bug with ToC generation where issue numbers had leading 0s
Merge branch 'phase2b' of github.com:DOAJ/doaj into phase2b
bump the number of retries on connection pool errors to 50 - let's make sure this doesn't become an issue for bulk operations
fix bug to allow issns to be used as ids for tocs
add root toc page which lists all the journals in the doaj, and a noscript from the search page which leads there.  Some enhancements to the dao es iterator to support this.
add jinja template for root toc page
add sitemap generation, associated route and caching features
fix layout bug with authors on toc
add sitemap generation script itself
add placeholder cache directory, and bugfix settings
remove EzID option from application form
all forms: change ISSN labels
application form: change help text of platform question
journal management: decouple in/out of DOAJ from editing other metadata
fix sorting of volume numbers to use correct string, and not integer representation
Merge branch 'phase2b' of github.com:DOAJ/doaj into phase2b
add by-start-page sorting to articles in toc