Added detector image to SubframeRefiner

• Significant refactoring of GUI to reduce code duplication, specifically in the code involved in implmenting a DetectorScene in a frame. The controls and image are now wrapped in a new DetectorWidget, which can be more easily added to new frames.
• DetectorWidget in SubframeRefiner has some unique functionality: upon clicking "update peaks" it clones the predicted peaks collection locally and updates the original predicted collection, allowing the user to visually see the effect of refinement on the peak centres.
• A DetectorWidget includes 3 default control widget: the QSpinBox and QScrollBar to cycle through the frames, and a QComboBox to change the set of images (DataSet). There are three optional controls that can be implemented with a simple boolean flag in the constructor, an interaction mode QComboBox which allows users to add selection boxes, masks and plot cross sections along lines, a cursor mode QComboBox which allows the user to change the unit of the tooltip showing the coordinates of the pixel under the cursor, and a QSlider to change the intensity scale.
• Removed now-unnecessary class ImagePanel (from SubframeExperiment) and unused LoggerPanel.

Resolves #329 (closed) and #170 (closed)