0.7.0: assenza con date, conto alla rovescia del boost, catalogo rifatto

- AwayDialog.qml: popup con inizio e fine (Dialog, ValueButton,
  DatePickerDialog: componenti e proprieta' verificati nella guida Silica
  dell'SDK). Il tasto Assenza apre il popup invece di mandare il comando;
- conto alla rovescia 30:00 -> 00:00 in Home e in copertina, con i secondi
  dell'impianto (AiraJson::countdown + timer che si riallinea a ogni lettura);
- commandPayload accetta campi extra (start/end);
- catalogo: lupdate leggeva solo i C++ e marcava 151 voci QML come obsolete.
  Ora src e qml espliciti: 197 stringhe, 0 non tradotte;
- versione 0.7.0 (spec, main.cpp), PROTOCOL, README/PIANO, post per il forum.

README.md

@@ -17,6 +17,14 @@ status, domestic hot water, and the house target temperature per zone.
   target) side by side and **tappable**, and three quick actions — boost, away
   mode and the plant commands, each with its own icon. It fits without scrolling
   — the controls live in their own pages
+- **Boost countdown**: while a hot water boost is running the home screen shows
+  it ticking down from 30:00 to 00:00, and the cover page shows it in place of
+  the hot water target. The seconds come from the plant's own boost end time, so
+  the count is right even if the boost was started from somewhere else
+- **Away mode with dates**: tapping *Away* opens a dialog where you pick the
+  first and the last day (calendar, one tap each). The house is kept at 15 °C
+  for that period and resumes its normal programme on the day you chose as the
+  last one
 - **Setpoints** page: house target and hot water target, each with the value the
   plant is keeping right now, a slider (the proposal, the plant value does not
   move), a row of quick values for cold fingers and a confirmation button that