Nionswift-instrumentation

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- Improve multiple shift EELS acquire by allowing disabling of dark subtraction and alignment.
- Synchronized acquisition now attached session metadata to resulting data items.

Thanks to Isobel Bicket/McMaster University for multiple shift EELS contributions.

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- Compatibility with nionui 0.5.0, nionswift 0.15.5.
- Fix issue with large SI's in wrong storage format (ndata vs h5py).

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- Add ability to pass some metadata from camera to final synchronized acquisition data. Temporary.
- Fix issue where record did not work after running synchronized acquisition.
- Add camera base methods for setting and clearing gain reference images.

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- Fix issue with probe position graphic when multiple channels enabled.

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- Fix issue with metadata in scan recorder result data items.
- Fix issue with spectrum imaging panel Acquire button not getting enabled.
- Rework MultiAcquire to use new partial data item updates.

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- Add section-by-section drift correction during synchronized acquisition.
- Add support for specifying drift correction parameters (only used in synchronized acquisition).
- Add record_immediate function for scan devices.
- Add partial updating during synchronized acquisition.
- Add optional help button and ability to register delegate for camera panel to handle.
- Fix numerous issues handling the subscan and beam position graphics.
- Fix issue starting scan record immediately after another one.
- Fix issue with reloading scans with leftover probe/subscan graphics.
- Enable spectrum image acquisition for MultiAcquire.
- Removed y-shift and shifter strength from MultiAcquire.
- Added a time estimate to MultiAcquire.