Center crosshair initially

Summary: Use current plane geomety to center crosshair

Test Plan:
manual testing

1. open MITK, load an image
2. close the Standard Display, open the MxN Display
3. see how the crosshair is centered
4. move the crosshair, reinit the node
5. see how the crosshair is centered
6. add render window widgets
7. see how the crosshair is centered only for the new render windows
8. test with multiple images loaded

Reviewers: s434n, O3 MITK Reviewer Group II

Reviewed By: s434n, O3 MITK Reviewer Group II

Subscribers: s434n, kalali

Maniphest Tasks: T29515

Differential Revision: https://phabricator.mitk.org/D791