Add change log for Qt Sensors 5.6.0 release.

Change-Id: Iafe6f3c2209156b5719352c0172749014a6d2b91
Reviewed-by: Lorn Potter <lorn.potter@canonical.com>

dist/changes-5.6.0

+Qt 5.6 introduces many new features and improvements as well as bugfixes
+over the 5.5.x series. For more details, refer to the online documentation
+included in this distribution. The documentation is also available online:
+
+  http://doc.qt.io/qt-5/index.html
+
+The Qt version 5.6 series is binary compatible with the 5.5.x series.
+Applications compiled for 5.5 will continue to run with 5.6.
+
+Some of the changes listed in this file include issue tracking numbers
+corresponding to tasks in the Qt Bug Tracker:
+
+  https://bugreports.qt.io/
+
+Each of these identifiers can be entered in the bug tracker to obtain more
+information about a particular change.
+
+****************************************************************************
+*                           Library                                        *
+****************************************************************************
+
+QtSensors
+---------
+
+ - Fixed minor documentation issues.
+ - Improved various examples
+ - [QTBUG-49741] Fixed hanging WinRT sensor plugin.