Revert "Deleted the video seekslider for a simpler usability of the ui. Added a filedialog for selecting the video and xml file to view."

This reverts commit 2180b014c9256e26abe187ffd4a539deb9b3ebc1.
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Revert "Revert "Deleted the video seekslider for a simpler usability of the ui. Added a filedialog for selecting the video and xml file to view.""

This reverts commit 1e77e27be815ac5e586e47c3438b9f2e7ec6c816.