5.0 m2 sorcer

These changes allow to configure capability classpath using maven artifacts, like this:

```xml
<platform>
	<capability name="cap">
		<version>1.0.0</version>
		<manufacturer>apache</manufacturer>
		<classpath>
			<entry>groupId:artifactId</entry>
			<entry>groupId:artifactId:version</entry>
			<entry>dir_or_jar_file.jar</entry>
		</classpath>
	</capability>
</platform>
```

<entry/> tag accepts coordinates with version or without it, in which case it uses <version/> value, as well as a path. This version should be backward-compatible and accept standard classpath format.

Also, this branch has changed access level of PlatformLoader.getDefaultPlatform() to protected, allowing it to be overridden.