Provide missing XML schemas for configuration files

[MartinLeidig]

We should provide XML Schemas for the project.xml and depend.xml configuration files.

[MartinLeidig]

Support for custom attributes in depend.xml: there are applications which add custom attributes to standardpage elements. The XML schema will support this by allowing any attributes from a namespace other than the target namespace, e.g. <make xmlns:myns="http://my-namespace" ...> <standardpage name="APage" xml="xml/frame.xml" myns:sitemap="true">

Applications adding custom attributes in the target namespace will have to put them in an extra namespace.

[MartinLeidig]

The depend.xml schema will also allow custom elements from other namespaces than the target namespace, e.g. <make xmlns:myns="http://my-namespace" ...> <myns:someElement/>

[MartinLeidig]

The depend.xml schema still allows custom attributes in the target namespace at the page elements inside the navigation (as it's common use). We should try to make the complete navigation optional (see Ticket #111).

[MartinLeidig]

Giving depend.xml a namespace has too much side effects to implement it in 0.15, e.g. XPath expressions have to be adapted (within XSL and Java - the XPath API abstraction, etc.).

[MartinLeidig]

Provided a depend.xml schema without namespace, which can be included using noNamespaceSchemaLocation xsi:noNamespaceSchemaLocation="http://www.pustefix-framework.org/2008/namespace/xml-generator-config.xsd"

[MartinLeidig]

still to do: schema for project.xml

[MartinLeidig]

Added schema for project-config. Now all config files have schemas.