Redirect improvements & consistency

Added

• Set "kv-user" cookie on sign-in and registration
• Implement handling of redirects on login/logout
• Go to login immediately after password reset

Changed

• Pass around search params on redirects
• Autofill email for change password form
• Form handling function can now set input values and readonly state
• Support /login?redirect=url in _redirects
• Set cookie params in consts.js
• Do not specify custom elements version in CSP
• Update to custom elements @ 1.4.3 (same hash somehow)
• Use standard redirect function, checking url.hostname
• Change document.title base on actions