fixed issue where scroll panel did not work on windows phone 8.1 update
but worked fine on windows phone 8. Had to force getComputedStyle to
return a 3D matrix for the transform property by specifying a non-zero z
value (-1px). We now detect the device density correctly for ie10/11 (we
use the screen object). We do not try and detect ie11 user agent, we
assume if using ie11 that the meta tag ie10 compatibilty is set. User
agent strings for ie11 are now even more complex. They specify webkit,
iphone, gecko etc etc as part of the string. This makes OS detection
more difficult using the user agent string.