Split set/unset, improve newline handling

[NoDiskInDriveA]

• splits set and unset so ws commands can revert to attributes to default
• unset: checks for existing attributes only at beginning of a line
• set: inserts a newline before a new attribute unless file already ends with one

[NoDiskInDriveA]

FYI the use case is resetting an attribute to default. Commands like xdebug feature as of now always require setting an override value to default. Also, if your override file doesn't end in a newline, attributes written get glued to the end of the last line, that's why I added a newline check/insert.