Concatenate: adjust description in Variable matching or allow matching variables with different roles

**What's wrong?**
The first option for Variable matching is described as "Treat variables with the same name as the same variable, even if they are computed using different formulae" where it should actually be "Treat variables with the same name _and the same role_ as the same variable, even if they are computed using different formulae".
If inputs have variables with the same name but different roles (e.g. feature in one input and meta in another) they will be renamed and appear in separate columns. A user may not always be interested in upstream assignment (and alignment) of roles. In that case, it can be hard to find out why the variables with the same name are _not_ treated as the same variable. Therefore, either "and the same role" should be added to the option description, or the matching in Concatenate should be tolerant to differences in role and convert all roles to a default (for instance: if the role is different, the matching always results in a meta variable - which can always be adjusted downstream)

**What's your environment?**

- Orange version: 3.37