Change language + change start/end of day + new button two weeks at a time + new options can be passed down

[JeremieSpiesser]

Hi davish,
First of all sorry for submitting multiple features in one go, i'll do better next time.
I added the following features to the plugin :

• ability to change the language
  To be precise, only the calendar columns (or grid in case of month) is translated. It doesn't change the buttons text (month, week, day). This means that only the month and day of the week are translated.
• added a button to see the events for two weeks
  Super useful on a ultrawide monitor !
• Ability to set the start and end day