Merge remote-tracking branch 'origin/feature/2389_resolution_sequential_fitting'
Merge remote-tracking branch 'origin/bugfix/8509_Fix_LoadAscii_Header_Skip'
Re #8239. Remove unused undo stack code.

This is inherited code from qtiPlot that was disabled on our
side a long time ago. It provided undo functionality on matrices.
Re #8329. Remove unused undo/redo action.

This hooked up undo and redo actions to menu items, but these menu
items are long-since removed from MantidPlot. The functionality had
also gone from Matrices, but is still there via the keyboard shortcuts
in Notes (if anyone would ever use it anyway).
Merge branch 'feature/8239_unused_undo_redo_code_applicationwindow' into develop