ext.popups.core.js: Whitespace cleanup

Change-Id: I861ba996cce9e9baf65e0630b1c2187d15df22b6
Prettify the embedded SVG code

* Do not escape double-quotes in single-quotes string
* Remove repeated <defs/> tags, one is enough
* Reindent

Change-Id: I6a5b53384b8d5604bee11cb993d040282accf999