Multi-device test support

 - Version 8.17.0
 - Added special serialno 'all' to run tests on all connected devices
Added default multi-device option value
culebron: consider status bar (local) in window height
Improved touch of ListViews

 - Added Culebron.targetViews
Added units to long touch

 - Version 8.17.3
 - Improved documentation
 - Changed PIL to Pillow on OSX
Corrected help message
viewclient: fixed problem with touch() call

touch() was called without named parameters which caused problems
in case device orientation was different than '2'.

Signed-off-by: Milosz Wasilewski <milosz.wasilewski@linaro.org>
Merge pull request #115 from mwasilew/master

viewclient: fixed problem with touch() call
#60: View.touch(self, type=.DOWN_AND_UP) --> touch(self, type=.., px=50,
py=50)

 - Version 8.18.0
 - Implemented by using delta instead of percentage
Minor changes
Bump

 - Version 8.18.1
merge--upstream