Fix "Write Script Online"

* Add similar code to `script.js` controller to let all controllers know it's a `new` route.
* Add similar *(nested function calls)* code to `routes.js` to indicate `new` script route.
* Add existing `newScript` checks to view ... **NOTE**: Possible naming consistency issue across the board here with preexisting identifiers.
* Continue using `editScript` as a complete catch-all... pre-existing condition... reorder a bit for some efficiency.
* Eliminate extra `pageMetadata` call
* Change `getExistingScript` to test req parm `new` instead of possible `scriptname` that could be absent.

Refs:

* #150
* https://openuserjs.org/discuss/No_more_new_scripts_possible