cubicweb-vcwiki #3529518 add a form and a ccplugin to setup a wiki [validation pending]

Following README instructions is error prone. It'd be nice to have a ccplugin command to add wiki to an instance.

priorityimportant
typeenhancement
done in0.2.0
load0.500
load left0.000
closed by<not specified>
patchAdd a command plugin to ease VCWiki creation [applied]