Starting with 5.0-rc16, tag types do not have a so-called
'min_role_id' any more`, but rather a set of roles exactly like a
person this impacts the way accessors are defined, as
'define_accessors' does not support min_role_id anymore in addition,
there was a rather confusing redundancy between 'min_role_id' and
'set_roles', as the latter was used for implementing the access rights
to the 'Set' method

If you have defined accessors local to your site in Accessors_site.py,
that actually use the min_role_id feature, then here is how to tweak
them from this release on.

If you want to keep the same kind of behaviour, just replace
min_role_id with set_roles as per the table below

min_role_id 	|	set_roles
------------------------------------
10		| ['admin']
20		| ['admin','pi']
30		| ['admin','pi','user']
40		| ['admin','pi','user','tech']

Now you might wish to take advantage of the new flexibility instead.

Also please note that 'node' is now an explicit role, so if e.g. a
slicetag needs to be set from the node directly, then it needs to have
the 'node' role as well.