Allow for Builder override.
Add artifact callback support.
Added constant for all "interesting" artifact suffixes (see ceylon/ceylon-common#35)
Allow to set callback per thread.
Add javadoc to ArtifactCallback, fix InputStream handling.
Provide a method to return the node content store display string
Provide node full name, content store in start(), and file in error()
(in order to clean any uncomplete file)
Added optional target 'module-resolver-api.jar' to build.xml