cubicweb-vcwiki #3780316 Limit the size of vcwiki names [validation pending]

So that we do not get ridiculously long urls and have a decent widget to edit it.

priorityminor
typeenhancement
done in0.2.0
load0.100
load left0.000
closed by#efbf8c7a3922 [schema] Limit wiki name size to 128 characters.
patch[schema] Limit wiki name size to 128 characters. [applied]