Add extension points to XML schema definitions where feasible

[david]

just some <xs:any namespace="##other" /> declarations where it fits. right now, at least inside <configurations> so we can have inline XSL stylesheets, for instance. others will follow, see #515.

[david]

(In [1907]) finished work on XSL support in config files. an XSL stylesheet may now also be embedded in the document and referred to by it's ID in the processing instruction. also refactored the XSDs a lot, they now use inheritance for the root elements and contain a first extension point for foreign namespaces inside <configurations>. closes #509 and refs #515

[david]

(In [1930]) allow attributes from any foreign namespace on document element of configs, refs #515

[david]

(In [1934]) allow attributes from ##any namespace (that includes local ones), refs #515

[david]

I guess we'll have more for 1.0

[david]

#519 is related to this

[david]

#795 could use something for that in the routing!

[david]

And maybe something for attributes from any namespace on <configuration> elements, as #710 proposes for these matched-or-not-flags

[david]

(In [2579]) Allow attributes from any namespace on <configuration> nodes, refs #515

[david]

(In [2580]) Allow any element from other namespaces in routing <configuration> elements, refs #515 and #795

[david]

(In [2648]) merging in branches/david-xml_only_config_system, kudos to impl for helping so much with this one :> please test it thoroughly; more work on migration of other config handlers will be done over the next couple of weeks. refs #519, #462, #710, #515