Use data registry to access paths and save pipeline runs

[joezuntz]

This adds an interface to the data registry. We want to:

• [x] Get paths to overall_input in yaml files using a direct lookup of a file by ID or name.
• [ ] Support looking up a file from a specific user or project.
• [ ] Support lookup by alias when ready.
• [ ] Support getting an input using its tag and a previous execution lookup.
• [ ] Add a way to save an execution entry from an entire pipeline run and its outputs.

[codecov[bot]]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (25def53) 89.81% compared to head (a7f921d) 89.66%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #93 +/- ## ========================================== - Coverage 89.81% 89.66% -0.16% ========================================== Files 16 16 Lines 1709 1722 +13 ========================================== + Hits 1535 1544 +9 - Misses 174 178 +4 ``` | [Files](https://app.codecov.io/gh/LSSTDESC/ceci/pull/93?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LSSTDESC) | Coverage Δ | | |---|---|---| | [ceci/pipeline.py](https://app.codecov.io/gh/LSSTDESC/ceci/pull/93?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LSSTDESC#diff-Y2VjaS9waXBlbGluZS5weQ==) | `84.88% <73.33%> (-0.35%)` | :arrow_down: |

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[stuartmcalpine]

I have updated the registry setup to the latest dataregistry interface syntax.

One technicality is during data_registry_lookup you can search for a dataset by name, and check it is unique. names dont have to be unique in the registry, name + version does, so we can come back to that