[ContextMenu] Regression - Android crash

Android crash, regression

• Made sure we save the correct instance of context menu button (#326)

[ContextMenu] Fixed app crash

Fixed

• Fixed a bug that occurred when people navigate out of the page with the context menu and send the app to background, it crashed when they reopened it.

[ContextMenu] Improvements to Context Menu

Improvements to Context Menu

• Android does not crash if you set an icon to the context menu button/control.
• Context Menu will now disappear when people send the app to background

Added DateTimeFormatter

Added DateTimeFormatter (#323)

* Created DateTimeFormatter

* Update DateTimeFormatter.cs

* Update DateTimeFormatter.cs

* Update DateConverter.cs

* Added comments and defaults

* Added methods with CurrentCulture

* Update TimeConverter.cs

* Update TimeConverter.cs

DateTimeFormatter PRERELEASE

v10.2.1-pre003

Added comments and defaults

DateTimeFormatter prerelease

v10.2.1-pre002

Update DateConverter.cs

PRERELEASE

DateTimeFormatter

Added icons to Context Menu

Context Menu

• Added icons to context menu items, documentation](https://github.com/DIPSAS/DIPS.Xamarin.UI/wiki/Popup-context-menu#icons).
• Added ability to select built in native iOS system symbols or android resources as icons for the context menu items, documentation

Context Menu

Context Menu

• Added a new ContextMenuButton and ContextMenuControl. These lets a user pop up a native contextual menu anchored to the button / view. Documentation can be found in the wiki.

Context Menu (pre release)

Context menu changes

• Made sure an single checkable item can not be unchecked
• Made sure the context menu button is transparent when used in the context menu control