Fix loading of all sensorgesture plugins.

After the change in qtbase 732dcfe7, only the first
sensorgesture plugin was actually being loaded.
Since the FILE argument of Q_PLUGIN_METADATA is optional,
removing that and the json file fixes the following bugs:

QTBUG-31900
QTBUG-31901

Change-Id: I7c0b67605a8fe680c37639f08926140e137dbe66
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Merge remote-tracking branch 'origin/release' into stable

Change-Id: I451682790ba1949c150d4045baf9df0cd467d486
Freefall gesture needs to be initialized into plugin to be usable

This fixes the flaky unit test failures. It also adds freefall to
unit test.

Task-number: QTBUG-32108
Change-Id: Ia1ee852b1e57b937fd7368073e259a139da9a697
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>
Merge branch 'release' into stable

Change-Id: I08bb0d6a9d4b0dddf76f463c32b3a4efdd632f0d
Initialize active variable in doubletap gesture

Fixes flakiness.

Change-Id: I6e8beaf5106c4dd1e26c3bf038ba9e394d0f080d
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>
Merge branch 'stable' into dev

Change-Id: Id44a93ddf8dc778f44e9684842a759d585558ee4