Start a different handling of the "implicit namespace" (now takes all frames *starting* from the calling frame into account). There's one remaining issue with warnings in `PoissonGroup`.
Only check functions for a _arg_units attribute when generating the implicit namespace.
Simplify the code path for setting and getting state variable values. VariableView now calls functions in the device instead of going back to the group. This should also allow straightforward implementation of missing features in standalone (e.g. setting/getting variable values with array indices, automatic loading).
Work around warnings in `PoissonGroup`.