Add AstXml writer

Previously phpDocumentor2 generated an XML file that was interpreted by the XSL based
templates to generate the HTML representation. With the current refactoring this has disappeared
and a new writer is introduced to still generate that XML for those who want it
Moved commands to their respective components
Update config with new settings
Add i18n to ParseCommand and clean up

During this commit I have attempted to make the ParseCommand more readable and
at the same time add internationalization to the command. By moving all strings to
a messages table and addressing those using a code it is possible to reduce the size,
 and increase the readability, of the configure method.