Fix a todo: InformationPanelContent::configureSettings code is moved to InformationPa...

Fix a todo: InformationPanelContent::configureSettings code is moved to InformationPanel::contextMenuEvent

Summary:
Fix a TODO : InformationPanelContent::configureSettings code is moved to InformationPanel::contextMenuEvent
Adding necessary accessors and changing visibility of one slot.

Test Plan:
1 compile
2 in dolphin right on the information panel
3 toggle preview
4 from the same context menu, click configure, metadadata settings appears
5 toggle "condensed date" if available

Reviewers: elvisangelaccio, #dolphin

Reviewed By: elvisangelaccio, #dolphin

Subscribers: kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D19832