Redesign of the admin interface.

Main changes:
 - Splitted up settings and users into two separate pages.
 - Added verified shield when the e-mail address has been verified.
 - Added the amount of personal items in the database to the users overview.
 - Added Organizations and Diagnostics pages.
   - Shows if DNS resolving works.
   - Shows if there is a posible time drift.
   - Shows current versions of server and web-vault.
 - Optimized logo-gray.png using optipng

Items which can be added later:
 - Amount of cipher items accessible for a user, not only his personal items.
 - Amount of users per Org
 - Version update check in the diagnostics overview.
 - Copy/Pasteable runtime config which has sensitive data changed or removed for support questions either on the forum or github issues.
 - Option to delete Orgs and all its passwords (when there are no members anymore).
 - Etc....

src/db/models/organization.rs

@@ -255,6 +255,10 @@ impl Organization {
             .first::<Self>(&**conn)
             .ok()
     }
+
+    pub fn get_all(conn: &DbConn) -> Vec<Self> {
+        organizations::table.load::<Self>(&**conn).expect("Error loading organizations")
+    }
 }
 
 impl UserOrganization {