New QGraphicsImageView class

Created QGraphicsImageView class to extend QGraphicsView, which mainly
shows 2D QImage as the main scene.

Initial function is showing an image and expand it to fit the
LargestPossibleArea (the whole image).

QGraphicsImageView uses QGraphicsImageViewPrivate class to keep the
header simple.
UI changes

QGraphicsView was promoted to QGraphicsImageView in the QtDesigner.

Right panel becomes a TabWidget:
1) DICOM header list tab
2) LUT tab
Added QGraphicsDICOMView

Replaced QGraphicsImageView withQGraphicsDICOMView. It’s better
specialisation of QGraphicsView class.
DICOM Tag list development

Trying to populate dicim tags in a TableWidget. To be continued.