Runtime configuration of reconstruction algorithm

[mlincett]

Presently, reconstruction algorithms have some hardcoded behaviors that we may want to configure at runtime. For example, the number of tested vertex positions.

In some cases, these can be tuned with environment variables (like the "mini" scan configuration, see start_scan.py).

We can think of a scenario in which we pass an additional string (JSON?) as config for the reconstruction algorithm.

[ric-evans]

This sounds like a reasonable need. I imagine there will be some settings for reco X that would not be apply to reco Y. I propose using a single dedicated CL arg, like --reco-algo-config that will take key:value pairs (similar to --nsides). This avoids the overhead transferring and persisting small config files.

For SkyDriver, the user can provide a dict.