logilab-database #151507 unique indexes: accept index name [validation pending]

building index names from columns can be lossy let's allow the caller to provide its own compact mapped index name

prioritynormal
typeenhancement
done in1.11.0
load1.000
load left0.000
closed by#e1ed19a8d6dd unique indexes: take an index name
patchunique indexes: take an index name [applied]