rename elx-keywords{ => -list}

The respective function from lisp-mnt also has the -list suffix.
lm-keywords on the other hand returns a space separated string
of all keywords.
elx-summary: rename argument STANDARDIZE => SANITIZE
elx-remap-keywords: re-indent doc-string
elx-keywords-list: add optional arg SANITIZE

Only remove/replace keywords if it is non-nil.
elx-commentary: add optional arg SANITIZE
elx-keyword-list: return strings like lm-keyword-list