Revision 2817

Changed a few places in Thuban and Extensions to convert wx
strings to internal string encoding. 

* Thuban/UI/classgen.py: Checked for return strings from wx problems.
Added one clarifing comment, removed two unused variables.

* Thuban/UI/mainwindow.py(OpenSession, SaveSessionAs, TableOpen): Using 
internal_from_wxstring for the pathname.

* Thuban/UI/tableview.py(doExport):  Using internal_from_wxstring
for the pathname.

* Thuban/UI/view.py(MapCanvas.Export):  Using internal_from_wxstring
for the pathname.

* Extensions/bboxdump/bboxdump.py(OnSelectFilename),
Extensions/export_shapefile/export_shapefile.py,
Extensions/gns2shp/gns2shp.py, Extensions/importAPR/importAPR.py,
Extensions/svgexport/maplegend.py, Extensions/svgexport/svgsaver.py,
Extensions/umn_mapserver/mf_import.py: Using
internal_from_wxstring for the pathname.