Keep special __file__ variable when clearing Python locals...

in MantidPlot.
Refs #10012
(cherry picked from commit eb4b296f8b9aef9388106591153b2b09c8d8bb72)
refs #9956. IDF Params corrected

Checked the params against all those provided by Max.
(cherry picked from commit dfb8e87edfa0309fc7f00e7f200ada62f4fe0787)