Add a option to start week on Monday

According to ISO 8601 the first day of a week is Monday. Many people prefer their calendars to start the week on Monday and most smartphone calendar applications (both in iOS and Android) offer this option.

Launchpad Details: [#LP1639843](https://bugs.launchpad.net/bugs/1639843) Antonio Camargo - 2016-11-07 15:54:02 +0000

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