Edit users page

Summary

Added the "Edit users" page.

Complete changelog

Added

• End borrowing validation
  • A user can't confirm the return of its own borrowings.
• Edit inventory view
  • Minimal width of tables for better responsiveness.
• Edit users view
  • Layout.
  • Errors displaying.
• Edit users controller
  • Users updating and deletion.
• Edit users validation
  • Check for admin self-modification.

Removed

• Edit inventory view
  • Hiding of some elements for small viewports.