Test that the "local" flag is being respected

[sjdv1982]

With the recent update in scratch and fingertipping, it must be made sure that local transformations are indeed still executed locally. A low-level test must be added. In addition, it must be verified that "local" interacts well with remote expressions (#237). Perhaps cells must also have a "local" property, disabling remote expressions / structured cell joins for them. And adapt transformer translation accordingly.