Generated background-image property formatting shouldn't use quotes

Motivation

Original report from Jouni:

Currently the generated CSS format is the following (after processing):

background-image: url('img/foobar.png');

Although the format is correct, the single quotes actually break the CSS in some major browsers.

So the correct format would be this (as valid as the above version, but works in all major browsers):

background-image: url(img/foobar.png);

While single quotes in CSS don't break rendering in major browsers, it still may be useful to control the type of quotes used for the generated background-image properties.

Implementation

Add an invocation-time parameter called --css-quotes for command line and cssquotes for Ant that will control the type of quotes SmartSprites should use in the generated background-image properties. The parameter will allow three values:

• SINGLE (default) – use single quote characters (')
• DOUBLE – use double quote characters (")
• NONE – use no quotes at all (as suggested by Jouni)