add off button
change buttons order
switch off the PopupSwitchMenuItem
display the icon
setting
improve session count display
Merge pull request #11 from Nicolas01/OffButton

Add an Off Button in the DialogWindow.
bug fixed: allow to reset counters and timer only outside of a break
remove Math.ceil, useless because multiplication of integers always give integers
reset time spent when the timer duration is changed
use unicode characters instead of special ones
Merge pull request #12 from Nicolas01/DisplayIcon

An option to display the pomodoro icon in the applet panel.
Replace the way the session count was display «[00]» by a lighter form «0·»
Merge pull request #14 from Nicolas01/BugOnDurationChanged

Bug on duration changed
Merge pull request #13 from Nicolas01/BugNoSound

Bug: no timer sound after reset during a break