[OpenSER-Docs] module documentation sgml to xml migration

Hello, many thanks to Edson for scripts and Henning for help and testing, the first phase of migrating the sgml to xml is done. You can now add changes to any module documentation you wish. Remaining steps, that should not affect the content: - migration from entities to xinclude (Henning perhaps we can talk a bit on IRC as I get some strange errors, if you have a bit of time) - decide about some parts of the documentation if we keep it or not. docbook xml tools are more advanced than sgml ones, more information is displayed now: e.g., svn revision info appears in each document now, should we keep it? It is not really what one will expect from revision part of a document (should show changes done in the document) As now, there are few other sgml documents. The templates for module documentation. Should we keep them (doc/templates/module)? I think they were not in use for quite some time, nor updated. The tls doc will be migrated xml (tls/doc). The rest should be now all over xml. Cheers, Daniel