#3 grammar improvements

[holger]

* current grammar has a sqname but now namespace definition, I suggest to drop sqname but use a unquoted charactersequence as constant term

* current grammar has all datatypes exlplicitly _date, _string etc. I suggest to have it a bit more generic, i.e. '_' alpha+ '(' termlust ')'.

[baz bishop]

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The second point can also apply to built-in predicate names.