Add "Open/Close" API to picker controls

[PureWeen]

Description

Currently the only way to open/close picker controls is to call focus/unfocus. This is non intuitive and requires you to have to wire up odd behavior at the platform level in order to make this work.

(Public) API Changes

IPicker

Properties

API	Description
open	opens the pickers dialog.
close	closes the pickers dialog.

Usage Scenarios

<DatePicker Visible="false" x:name="picker" />

picker.Open

Backward Compatibility

N/A

Difficulty

Low

[maxiking01]

These function will be useful for Nullable DatePicker where a datepicker is hidden and should be opened when user clicks the control. So far the Nullable DatePicker was implemented using Focus, UnFocus function.

[mos379]

Adding my support here! Really need some possibility to show a hidden picker on windows and ios

[SmartSquareAZ]

Is there progress on this topic? This function would be very nice!

[FreakyAli]

+1

Willing to work on this myself if I have to,

@PureWeen can you confirm what's needed here?