jquery.spinner: Fix small issues

jquery.spinner: Fix small issues
(Follows-up r95445)
* Using the same spinner as before, preserving svn history (20px vs. 16px)
* Adding a line-break at the end of file and changing indentation per our conventions
* Adjusting doc to reflect the plugin itself instead of what it replaces.
* Using shorthand utility in jQuery (no / and using the attr-object as second argument)
* Adding @return comment to $.fn.injectSpinner
* Adding return statement to $.removerSpinner (returning a jQuery object of the element). Could be useful, but better than not having a return value at all.

JSHint:
* Adding parentheses around the class object property, otherwise it may be interpreted as a class operator which breaks the object.