Fix long click on Android

Android's uiautomator has a broken long click implementation.
uiautomator will not pause long enough on long click which causes Android to detect the long click as a normal click.

This fix uses reflection to access uiautomator's private touchDown/touchUp methods to reimplement longClick correctly.

In theory I should be able to obtain a reference to android.app.UiAutomation without using reflection. However this doesn't seem possible when using uiautomator. getInstrumentation().getUiAutomation(); doesn't work because we're not using instrumentation.
Merge pull request #1840 from bootstraponline/fix_long_click

Fix long click on Android