Fix rendering of polylines and polyrings after tileLevel refactoring

Summary:
The textureLayer's tileLevelChanged signal was never forwarded to the geometryLayer, which made placemarks and text show up, but no areas or lines.

I tracked this down to the refactoring regarding the tileLevel from december 3rd in commit f847505b02940aff9e37a6fa2317a7098c078d97.

Test Plan:
environment: linux64, qt 5.8 or 5.9 (both tested)

i just opened "germany.kml" from the examples/kml folder in marble-qt: without the fix only the pin and text shows up, with the fix, the area below is highlighted in red with a yellow outline.

Reviewers: Marble

Subscribers: Marble

Tags: Marble

Differential Revision: https://phabricator.kde.org/D6072