Fix altitude restriction log and allow restriction down to -15 degrees

Summary:
Fix Scheduler log for altitude restriction.
Lower minimum altitude restriction from 15 degrees to -15 degrees.

Test Plan:
Make a schedule job trig the restriction and observe the correctness of the log in the Scheduler console.
Configure a restriction down to -15 degrees and observe as Scheduler properly honors the limit.

Reviewers: mutlaqja, wreissenberger

Reviewed By: mutlaqja, wreissenberger

Subscribers: kde-edu

Tags: KDE Edu

Differential Revision: https://phabricator.kde.org/D20058