SPI permitting new classpaths to be constructed and registered.

{@link org.netbeans.spi.java.classpath.ClassPathProvider}s can be registered to default lookup in order to associate information about classpaths with files. For example, a Java-oriented project type would normally indicate that its Java sources have a certain classpath associated with them.
For a source file the ClassPathProvider has to return a {@link org.netbeans.api.java.classpath.ClassPath} of the following ClassPath types:

- ClassPath.SOURCE - the classpath contains the source roots of the project
- ClassPath.BOOT - the classpath contains the jdk runtime libraries
- ClassPath.COMPILE - the classpath contains the project compile libraries (compile classpath)

it may also return a ClassPath of type ClassPath.EXEC pointing to the build output folder.
For build output the ClassPathProvider has to return a ClassPath of the following types:

- ClassPath.BOOT - the classpath contains the jdk runtime libraries
- ClassPath.COMPILE - the classpath contains the project compile libraries (compile classpath)
- ClassPath.EXEC - the classpath contains the build output folder

{@link org.netbeans.spi.java.classpath.ClassPathFactory} may be used to create new {@link org.netbeans.api.java.classpath.ClassPath} instances.