dont save/restore window configuration for frames with (persp-ignore-wconf . t) parameter
fix #5. Show correct error when trying to rename none persp.
Allow to customize name of nil persp.
fix persp-rename and persp-remove-from-menu
rename "none" persp to nil
Merge branch 'test-ignoring-wconf-save-restore-for-frames-with-parameter'
fix #6. Add customizable filtering of what buffers to save.