Transformers have no (or incosistent) attribute "id_db" assigned

[gplssm]

• Use it to differentiate multiple transformers in the same station

Tasks

• [ ] rename to "id" (if there are no major conflicts/broken dependencies)
• Change 6 places in the code where transformers are instantiated

The change was requested by #312

[gplssm]

I decided it's not worthy to rename the attribute to id.