Tuning the TouchExplorer

1. Tuned the max angle between two moving fingers in touch
   exploration mode for a gesture to be considered a drag.
   The previous value was too aggressive and it was fairly
   easy for the user to get out of dragging state if she
   ingreases the distance between her fingers.

bug:5223787

2. Before clicking the explorer was sending hover enter and
   exit resulting in firing the corresponding accessibility
   events which leads to announcement of the content under
   the tap that triggered the click. However, the click is
   actually performed on the last touch explored location
   (if in the distance slop of course) instead of the actual
   tapping pointer location. Before fixing that the user was
   confused since he was hearing announcement of one content
   but actually was clicking on something else.

bug:5225721

Change-Id: I79fec704878f98c95f181bf8a9647e0bb1bd10ef