Added M501 to load config-override
renamed old M501 to M502 as it should have been for removing config-override
Added M504 xxx to save to config-override.xxx
added load/save to load and save names config override files
Make Filestream open for "w" not "a"
Merge pull request #303 from wolfmanjm/upstreamedge

Added M501 to load config-override