Support WebSelections in WK2 on iOS.

https://bugs.webkit.org/show_bug.cgi?id=127015
<rdar://problem/15211964>

Reviewed by Benjamin Poulain.

This change adds support for text only (non block mode)
selections in non editable content.
The main changes consist in hooking up the new gesture type
and touches to handle selection creation and interaction.
It also includes changes to the way first responder is handled
which includes the implementation of the isEditable method
to allow iOS to know when to show the keyboard.

* Shared/ios/WKGestureTypes.h:
* UIProcess/API/ios/WKInteractionView.mm:
(-[WKInteractionView isEditable]):
(-[WKInteractionView canBecomeFirstResponder]):
(-[WKInteractionView webSelectionRects]):
(-[WKInteractionView _highlightLongPressRecognized:]):
(-[WKInteractionView _singleTapRecognized:]):
(-[WKInteractionView inputAccessoryView]):
(-[WKInteractionView canPerformAction:withSender:]):
(-[WKInteractionView _showDictionary:]):
(toWKGestureType):
(toUIWKGestureType):
(selectionChangedWithGesture):
(selectionChangedWithTouch):
(-[WKInteractionView selectedTextRange]):
(-[WKInteractionView webSelectionAssistant]):
(-[WKInteractionView _startAssistingNode]):
(-[WKInteractionView _stopAssistingNode]):
(-[WKInteractionView _selectionChanged]):
* WebProcess/WebPage/ios/WebPageIOS.mm:
(WebKit::WebPage::selectWithGesture):
(WebKit::WebPage::updateSelectionWithTouches):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@162582 268f45cc-cd09-0410-ab3c-d52691b4dbfc