yams #112914 add a script to compare two yams schema using a diff tool [validation pending]

add a script which orders schema entities properties and attributes
in a file

cf. https://www.cubicweb.org/ticket/464991

prioritynormal
typeenhancement
appeared in<not specified>
done in0.37.0
load1.000
load left0.000
closed by#701:b739d650ba6a
patchadd a script which compared two yams schema (closes #112914) [applied]