Use ha-tabs-subpage instead of ha-app-layout

[farmio]

Use ha-tabs-subpage and hass-tabs-subpage-data-table

Pros:

• this fixes the last row of the group monitor being out of the viewport (too low)
• header is smaller - on mobile even the search bar is at the most top of the viewport
• supports back button out of the box

Cons:

• rows are now the default height of 52px instead of 35px - I couldn't find how to change that yet
• sidebar menu is not shown in mobile view in favour of back button
  Update: This seems to be a non-issue as a side-swipe on mobile (app) should bring up the sidebar anyway
• No "KNX" header anymore. But I guess users will know what they navigated to anyway.

closes #89

New (9,5 telegrams / view)	Old (13 telegrams / view)