Added a save button to MantidDOck widget

Refs #10125
Added error handling, moved save button

Moves save button to prevent accidental deletion of workspaces

Refs #10125
Fixed small issues in MantidDock, improved save dialog

Refs #10125
Merge branch 'master' into bugfix/10125_add_save_button_to_workspace_list

Conflicts:
	Code/Mantid/MantidPlot/src/Mantid/MantidDock.cpp

Refs #10125
Merge remote-tracking branch 'origin/bugfix/10125_add_save_button_to_workspace_list'