Re #6000. Added FilenameDialogEditorFactory for QtPropertyBrowser
Re #6000. Tidied up custom property editors.
Re #6000. Added WorkspaceEditor factory for QtPropertyBrowser.
Re #6000. Wrong slash in a filename
Re #6000. One more wrong slash in a file name
Re #6000. Allow to unset Workspace attribute od TabulatedFunction
Re #6000. Fixing compiler warnings
Re #6000. Show an error message if attribute cannot be set
Merge remote-tracking branch 'origin/bugfix/6000_mantid_fit_crash'

Conflicts:
	Code/Mantid/QtPropertyBrowser/CMakeLists.txt
Refs #6000