Secure /users/*

Don't send sensitive data to client, remove unused delete:/users/:id.
Allows users to be queried using username
Rename dangerously shadowed select2OptionToIdNamePair -> select2OptionToIdUsernamePair
Grey out inactive users in select2's

* On search-page when kavi, and selecting classifier
* On subscriber-management-page, when showing and selecting classifiers
Admin can edit classification author

Also, extract meku.js:select2OptionToUser
Sort search-page results by registration date also if classifier selected
Root can edit classification.registrationDate

Can also clear it.
user-management: Prevent page from resetting to top when clicking search filters
search-page: Prevent page from flickering/scrolling when reloading drafts and recents
Merge pull request #47 from kavi-fi/random-fixes

Random fixes