[ticket/11314] Add recent bugfixes to editor.js and fix jshint issues

Bugfixes to editor.js that were added in prosilver seem to have been
forgotten in the acp editor.js. This has been fixed with this commit.
After the next few commits all editor.js files will be the same.
Additionally, the issues mentioned in the jshint report were fixed.

PHPBB3-11314
[ticket/11314] Fix issues mentioned in jshint report

Additionally, the editor.js files are now the same file in both
subsilver2, prosilver, and the acp.

PHPBB3-11314