Changes for Fusion compatability

Existing application does not work with Fusion due to different
implementation of collection function. Fusion does not return non-XML
content such as XQuery files which means the endpoints are not
found. There is also a function name clash in openapi-tests-simple.xqm
which creates an error in Fusion with the sample endpoints.

Issue is resolved with recursive functions that use xmldb functions  in
order to find child resources and collections to build the list of uris in
place of existing base-uri function. This works in both Fusion and eXist

There is also an extension to the list of recognised xquery file
extensions to cover other used formats.