Draft: Addon to apply user mask

It's come up a lot of times that more flexible masking would be nice. As a first step, how about an addon which can just be given an h5 file and will apply a mask found in there? The addon assumes that the h5 file will have a dataset consisting of [module, cell, ss, fs], with the first two being optional based on burstMode and multiModule. The reason to use one file for many modules (which will all compete to open it) is that that makes managed pipelines less painful.

As usual, would be nice with a robust way for devices (and their addons) to know their device-within-multi-module-detector index. Have copied some regexes from DetectorAssembler for now.

Here's the example of OndaBridge feeding data into OnDA (discussed yesterday with Ivette and Luca) but with a silly mask added in the Addonis devices:

Now, we need ordering to run this masking - probably first (so UserMask is bad name if we're lexicographically inclined). One way to add configurable ordering would be like this