(!Beta only!) Added polling intervals to NAS settings

Beta 3, details see here - please help with testing:

• ✅ improve device detection / auto-discovery (see discussions #164 and #171) → implemented and tested,
  
• ⚠️ add cache device info and cache disks (see discussion #161) → implemented, but not tested yet,
  
• ⚠️ add switching of cooling profiles / fan levels (see discussion #151) → implemented, but not tested yet,
  
• ⚠️ add changing of entity polling intervals in NAS settings (see discussion #181) → implemented, but not tested yet,
• ⚠️ reworked some code on the Example Dashboard Page to display cache disks and single pools → implemented, but not tested yet.