Modularize the xml-apis-ext dependency

[carlosame]

This project depends on the org.w3c.dom.svg package (and also a couple of org.w3c.dom.smil classes), as provided by xml-apis-ext-1.3.04.jar which also contains the SAC classes.

For modularization purposes, it is more convenient to depend on two separate packages, svgom-api and smil-api with their own module names. The sources of the xml-apis-ext-1.3.04.jar package are archived at:

http://archive.apache.org/dist/xml/commons/

although there are more recent versions of the package, 1.3.05 and 1.4.01 available from:

http://xerces.apache.org/mirrors.cgi#source

In principle this project is not using those sources, instead I downloaded the original Java bindings from W3C, although it seems that the classes in xml-apis-ext-1.3.04.jar are a mixture of SVG versions. I found the following source downloads:

• SMIL (old version): https://www.w3.org/TR/smil-boston-dom/java-binding.zip
• SVG 1.0: http://www.w3.org/TR/2000/CR-SVG-20000802/java-binding.zip
• SVG 1.1: http://www.w3.org/TR/2011/REC-SVG11-20110816/java-binding.zip

The following URL about SMIL 3.0 may also be relevant as a reference for the latest version:

https://www.w3.org/TR/SMIL3/smil-timing.html#DOM-SupportedMethods

I had to modify several API method signatures so they matched the implementations in EchoSVG. Although it would have been easy to upgrade EchoSVG instead, that would have created problems in cases where both xml-apis-ext-1.3.04.jar and svgom-api / smil-api are found in the classpath or modulepath (which is conceivable if somebody is using EchoSVG and Apache FOP in the same project).