Added support for twoFingerTap from XCUIElement spec
Added support for twoFingerTap from XCUIElement spec

Summary:
I have added support for the twoFingerTap from XCUIElement spec
Closes https://github.com/facebook/WebDriverAgent/pull/286

Differential Revision: D3882621

Pulled By: marekcirkos

fbshipit-source-id: 68af6341b6dda4f1fa73c3d4361874765a27d0f4

qa-dev/WebDriverAgent,calabash/WebDriverAgent,PiranhaTeam/WebDriverAgent,qa-dev/WebDriverAgent,zenzhu/WebDriverAgent,riccoyu/WebDriverAgent,drptbl/WebDriverAgent,PiranhaTeam/WebDriverAgent,qa-dev/WebDriverAgent,Gogle/WebDriverAgent,zenzhu/WebDriverAgent,PiranhaTeam/WebDriverAgent,Gogle/WebDriverAgent,riccoyu/WebDriverAgent,b1ueshad0w/WebDriverAgent,b1ueshad0w/WebDriverAgent,Gogle/WebDriverAgent,ymin/WebDriverAgent,ymin/WebDriverAgent,riccoyu/WebDriverAgent,b1ueshad0w/WebDriverAgent,qa-dev/WebDriverAgent,calabash/WebDriverAgent,ymin/WebDriverAgent,drptbl/WebDriverAgent,PiranhaTeam/WebDriverAgent,zenzhu/WebDriverAgent,b1ueshad0w/WebDriverAgent,Gogle/WebDriverAgent,calabash/WebDriverAgent,riccoyu/WebDriverAgent,drptbl/WebDriverAgent,ymin/WebDriverAgent,PiranhaTeam/WebDriverAgent