The filepath arg of the HDFArray() and TENxMatrix() constructors should accept a Hub ID #20

E.g. something like HDF5Array("HubID:EH1039") should work and "HubID:EH1039" should be stored as-is in the returned object.

This way serialized instances will work anywhere (every time the object needs to access the on-disk data, the path is expanded to the local cached file).

This would prevent this kind of problem: https://stat.ethz.ch/pipermail/bioc-devel/2019-September/015537.html