Refs #8745 Swapped file names and fixed some problems

refl_window and refl_gui have had thier names swapped to make more sense, as refl_gui was orinally the underlying window when actually being the interface wiht functionality would make more sense.

Discovered problems with the save, load and re-load functionality which I'm fixing.
Refs #8475 Save and Laod dialogs no longer throw on cancel

Before, when cancel was pressed on a save or load dialog it would throw an IOexception saying "file not found".

This was because the previous call was retrieving a string and when cancel was pressed that string was null. The script would then attempt to open whatever was in that string, regardless of the user pressing open/save or cancel.

In order to make it safer the dialog now calls the QFileDialog.exec_() in order to check if the user pressed Open/Save or cancel, then acts accordingly.
Merge branch 'feature/8475_Ref_GUI_UI_File' into develop