cubicweb #2067560 improve rql bar: add clean field button [open]

I would like to see a "wipe field" button right of the rql bar so that I can easily erase the current query (without erasing the X clipboard selection when selecting the query to erase it)

prioritynormal
typeenhancement
done in<not specified>
load0.100
load left0.100
closed by<not specified>