Fetch KConfig settings if they exist.

Summary: The settings were set, but never retrieved, thus misleading the user.

Test Plan: Recompiled and installed, started the Arduino settings from Embedded -> Arduino, and the saved settings were loaded.

Reviewers: kfunk, patrickelectric

Reviewed By: patrickelectric

Subscribers: patrickelectric, kfunk, kdevelop-devel

Tags: KDevelop

Differential Revision: https://phabricator.kde.org/D3567