Abstracts IPropertyGrid and uses in Preferences to fix a11c issues

[netonjm]

NOTES: Proppy doesn't expose any API to allow us remove the toolbar
xamarin/Xamarin.PropertyEditing#663

Also there is an issue in numeric decimal editors in Culture separator symbol non ENGLISH based
xamarin/Xamarin.PropertyEditing#662

Fixes VSTS #1003417 - Replace current F# format preference panel to use native Proppy
Fixes VSTS #1003416 - Replace current XML format preference panel to use native Proppy
Fixes VSTS #1002622 - Add a mechanism outside proppy to hide toolbar
Fixes VSTS #637121 - Accessibility: Preferences - Code Formatting: Unable to access Layout,Refracting,Spacing categorized formattings using keyboard.
Fixes VSTS #637246 - Accessibility: Preferences - Code Formatting F#: Not able to access Attributes,Document,Elements and it’s inside elements under 'Source code -> XML document'.
Fixes VSTS #1001600 - A11Y_Xamarin Designers_Property pane_keyboard : Keyboard is getting trapped at “Automatic tree” check box
Fixes VSTS #1001627 - A11Y_Xamarin Designers_Property pane_keyboard : User is unable to open the “Edit” button by using space/enter keys### Preferences CodeFormating XML
Fixes VSTS #1001625 - A11Y_Xamarin Designers_Property pane_keyboard : User is unable to check/uncheck the “Automatic tree” check box by using space key

Preferences CodeFormating F#

[netonjm]

Branch rebased and ready to review @sevoku

[netonjm]

@monojenkins rebase

[mrward]

Testing this the problems I ran into:

• Cannot tab into properties from XML and F# tab. (Similar problem with the View - Pad - Properties window)
• Voice over does not announce Table when the properties control is moved to from the XML and F# tab. It is not obvious from Voice Over that you can move inside the table since Table is not mentioned.
• The reset button (right hand side of a property) is read by Voice Over as Properties, image. Not obvious what this supports based on what Voice Over reads. (Same problem with View - Pad - Properties window).

Once you get inside the properties control everything seems good. Tabbing around is OK. Voice over works. Only problem is the the reset button/image being read as Properties, image, mentioned above.

[mrward]

Latest build problems:

• Cannot tab into properties from XML and F# tab. (Similar problem with the View - Pad - Properties window)
• Voice over does not announce Table when the properties control is moved to from the XML and F# tab. It is not obvious from Voice Over that you can move inside the table since Table is not mentioned.
• Voice over seems to only be reading a description for property value controls. It should be reading the associated label, then the full description. As an example currently it reads
  This checkbox is for the Identity on try/with Property. unticked, checkbox.
• I think it should instead read the label instead of a description. The description does not add anything and it should not describe the control type. Voice over should be saying something like: Identity on try/with. unticked, checkbox.. You should be able to do this by associating the check box with the label on the left hand side.
• The reset button (right hand side of a property) is read by Voice Over as This is the Property button for the Identity on try/with Property, image. Edit the properties for this editor. The description should not be describing the control type button. Should set an accessibility role here I think so voice over knows to say Press control - option - space to open.

[sevoku]

I've tried the latest build now too and see the same issues:

* Cannot tab into properties from XML and F# tab. (Similar problem with the View - Pad - Properties window)

I think this worked before, now proppy is not part of the focus chain at all.

* Voice over does not announce Table when the properties control is moved to from the XML and F# tab. It is not obvious from Voice Over that you can move inside the table since Table is not mentioned.

We should fix that, should be just a matter of setting a11y props on the table view.

@netonjm can we fix these two problems ^^?

The following issues are external in proppy, we should file them separately, but this shouldn't block this PR:

* Voice over seems to only be reading a description for property value controls. It should be reading the associated label, then the full description. As an example currently it reads
  `This checkbox is for the Identity on try/with Property. unticked, checkbox.`

* I think it should instead read the label instead of a description. The description does not add anything and it should not describe the control type. Voice over should be saying something like: `Identity on try/with. unticked, checkbox.`. You should be able to do this by associating the check box with the label on the left hand side.

* The reset button (right hand side of a property) is read by Voice Over as `This is the Property button for the Identity on try/with Property, image. Edit the properties for this editor.` The description should not be describing the control type button. Should set an accessibility role here I think so voice over knows to say `Press control - option - space to open`.

[sevoku]

@monojenkins backport release-8.4