Added more DatepickerOptions

Taken from online docs: http://bootstrap-datepicker.readthedocs.org/
From : https://github.com/borisyankov/DefinitelyTyped/commit/be638c57f89b42d1474243156980f45e1ddc9039#commitcomment-6817460 

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In the beginning of this [document](http://bootstrap-datepicker.readthedocs.org/en/release/options.html):

> All options that take a “Date” can handle a **Date object**; a **String** formatted according to the given format; or a **timedelta** relative to today, eg “-1d”, “+6m +1y”, etc, where valid units are “d” (day), “w” (week), “m” (month), and “y” (year).

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Perhaps add a comment next to the `online docs` link