give an heritage mechanism for models functions

[mingarao]

To do with function:lookup + config.xml

[emchateau]

We've tried it with @PhilPons, in a getModel function inside 'synopssx/lib/commons.xqm'.

But, it generated a FONS0004 error No namespace declared for prefix 'ampere.model.tei', as we were testing with a function-lookup if a QNamed function exists... (function-lookup only test QNames)

Have a look if it's possible to test if namespace exists before function-lookup.

[emchateau]

unworking exemple is available at https://github.com/ANR-Ampere/synopsx/tree/dynamicmodel

ANR-Ampere@fbb863f

[emchateau]

solved by @mingarao in 52bbda5
It suppose that user use the same naming pattern for models

[mingarao]

It now works if we use default function namespaces in models modules : #56
TO DO : take arity into account

[mingarao]

heritage ok but arity is not managed yet