daily reminder feature + comments

added a daily reminder feature.now the user has the option of activating
the daily reminder which reminds him of recording his expenses/incomes
every day at a user defined time.
Added classed and Activities : ReminderSettingsActivity ,
ReminderReceiver , AlarmService , TimeDialog (with comments)
Also added comments on OverviewActivity , ReminderSettingsActivity ,
SettingsActivity , CurrencyDialog , CalendarDialog