Inline View, Incr/Decr with Arrow Keys and Mouse

DateTimePicker can be added as an inline element by setting `isInline:
true`. Since DateTimePicker is added inline, input element should be
explicitly specified with `inputElement: <jQuery object of Element>`.
Check Example [Inline View](demo/View-Inline.htm).

Input Elements on DateTimePicker can be made read-only with
`readonlyInputs: true`.

Header of DateTimePicker Element can be removed with `showHeader:
false`.

Added functionality to increment or decrement values of dates using Up
and Down Arrow Keys as well as using Mouse Wheel.