This commit adds a documentation for the KIWI XML description.
In contrast to the former auto generated code from the XML
schema this document can now finally be used as a reference.
Along with that new chapter all auto generated and static
html content as been deleted. Also all helper scripts around
the proprietary oxygen tool and our schema doc generator
has been deleted. Auto generating this information does not
lead to a reference guide people can really work with.
As a consequence to these changes this commit also includes
some changes of the structure such that no information written
by other people in the past gets lost. This Fixes#1421
and Fixes#1474
The current design of the documentation does not allow for
continous improvement and development. It's missing a basic
structure and concept for documenting step-by-step workflows
and generic explanations.
Fix some minor inconsistencies due to latest code changes
with regards to py2 and py3 compatibility and also change
the style of the chapter to be more straight forward for
people who would like to contribute from scratch
