logilab-database #132587 add overideable dictionary on advanced helper for python -> db type conversion [validation pending]

this would allow to factor out some code from cubicweb, as well as properly overriding type conversion when needed (eg adding new base types)

prioritynormal
typeenhancement
done in1.10.0
load0.500
load left0.000
closed by#3c58962f468c add TYPE_CONVERTERS dict on advanced helpers defining conversions callback from Python SQL types (closes #132587)
patch[sqlgen] Allow to unprotect some parameters during the creation of an SQL INSERT query [applied]