App: Buttons for skipping +/- week

app/templates/main.html

@@ -12,8 +12,10 @@
 	<form id=f method=GET action="?">
 		<label for=date>Date:</label>
 		<input id=date type=date name=date step=1 value="{{ g.date }}">
-		<button type=button onclick="document.getElementById('date').stepDown(); document.getElementById('f').requestSubmit()">←</button>
-		<button type=button onclick="document.getElementById('date').stepUp();   document.getElementById('f').requestSubmit()">→</button>
+		<button type=button onclick="document.getElementById('date').stepDown();  document.getElementById('f').requestSubmit()">←1</button>
+		<button type=button onclick="document.getElementById('date').stepUp();    document.getElementById('f').requestSubmit()">→1</button>
+		<button type=button onclick="document.getElementById('date').stepDown(7); document.getElementById('f').requestSubmit()">←7</button>
+		<button type=button onclick="document.getElementById('date').stepUp(7);   document.getElementById('f').requestSubmit()">→7</button>
 		<select name=hours>
 			<option value=0{{ " selected" if g.hours==0 else "" }}>Study hours</option>
 			<option value=1{{ " selected" if g.hours==1 else "" }}>Working hours</option>