added /abs/path/settings.json handling

before this path, one could only supply a relative path like:
 --settings ../relative/path/settings.js
now one can also use it with absolute paths like:
 --settings /abs/path/settings.json
Update Settings.js

added brackets to match etherpad lite devs' coding style
Merge pull request #2184 from qknight/patch-1

added /abs/path/settings.json handling