Use controller throughout most worker code

[richfitz]

This PR continues the refactor, tidying up (incompletely) the use of con and keys through the worker code in favour of using a controller. This means pulling the special worker keys into the worker (which makes sense). Also added temporary new versions of more functions that use the new interface

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.83%. Comparing base (bf0c8fe) to head (cc7f311). Report is 4 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #109 +/- ## ======================================= Coverage 99.83% 99.83% ======================================= Files 34 34 Lines 2451 2472 +21 ======================================= + Hits 2447 2468 +21 Misses 4 4 ```

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