Y-inclination sensor value computation update

Fix #405

Test: http://jenkins.catrob.at/job/Catroid-custom-branch-no-emma-test/164/
http://jenkins.catrob.at/job/Catroid-custom-branch-no-emma-test/179/
http://jenkins.catrob.at/view/Catroid/job/Catroid-custom-branch-no-emma-test/218/