Attributes range could accept a set of chars

[cardinot]

The attr ranges could accept a set of chars. The attr ranges are mainly used by the plugins to define their attributes, e.g., see the attributes of this plugin.

The examples below could be supported:
"char{a,y,c,p}"
"char{a,z}"

For people interested in implementing it (hints):

• check the code for the set of strings at AttributeRange::parse