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

made sure to dispose properly for both platforms (#325)

[ContextMenu] Improvements to Android icon and auto-close when app go…

…es to background (#324)

* made sure android does not crash if you add a icon to a context menu item

* made sure we close the context menu when the app goes from background to foreground

* made sure we close the context menu when the app goes to background on ios

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

Added comments and defaults

Update DateConverter.cs

Update DateTimeFormatter.cs

Icon added to Context Menu Item (#321)

Added icons for context menu items

Added native Context Menu (#320)

Made sure single checkable items are not unchecked if the user tries …

…to uncheck them

made sure button in context menu control is transparent