add userAgent reporting
Added swipe test for 'swipeDown' strategy
Made clearing text faster on Android when there is hint text.

We try several approaches to clear text on Android and only check
for hint text at the end. This can be made faster if we check for
hint text after each clear attempt.
Also modified hasHintText() a bit to make it more reliable.
Merge pull request #3735 from 0x1mason/swipe_test

Swipe test
update appium-adb with getAdbServerPort method
Merge pull request #3785 from paymand/hint_text_detection

Made clearing text faster on Android when there is hint text.
Merge pull request #3622 from Jonahss/userAgent

add userAgent reporting
Fix for getContexts() on Selendroid.