adjust group type hint for User API response

fix User response object in API

API: make responses sortable

All responses now need to implement __toString() so they can be easily
sorted or printed.

API: initialize responses explicitly

Instead of passing unknown arrays, explicit parameters are passed.
Revision handling should now work correctly since we can pass revision=0
but a mtime.

Reworked API definition

This cleans up the API:

* no more compatibility with obsolete wiki API
* no more difference between wiki.* and dokuwiki.* calls -> core.*
* use of optional parameters avoids

Reworked API definition

This cleans up the API:

* no more compatibility with obsolete wiki API
* no more difference between wiki.* and dokuwiki.* calls -> core.*
* use of optional parameters avoids double definitions
* use Response objects for complex results
* always use named primitives as input
* major cleanup of docblock descriptions

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