Dvha

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- [Query] Allow user to define different database connections for each Group
- [Database] PostgreSQL users can export their DB to SQLite
- [Database] Export database to JSON
- [ROI Map] Only prompt user about ROI Map saving if it has been edited

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- [Error Logging] Implemented error logging, stored in ~/Apps/dvh_analytics/logs. Code borrowed from dicompyler.

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- [Misc] Remove references to the deprecated import_settings.txt file
- [ROI Map] Fix GH Issue [75](https://github.com/cutright/DVH-Analytics/issues/75)
- [ROI Map] Deleting a physician in the ROI Map module now actually deletes the .roi file stored locally
- [ROI Map] Alert user on ROI Map frame close that ROI Map won't be saved when using the OS's window close button
- [ROI Map] Prevent TypeError on editing physician name
- [ROI Map] Bug fix for validating new physician name

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- [Import] Only allow `DoseSummationType` of `PLAN` or `BRACHY` if multiple dose files are found
GH Issue [68](https://github.com/cutright/DVH-Analytics/issues/68).
- [Import] Bug fix: If multiple files are found for a plan-set, select only the latest file per
`os.path.getmtime`. Previously, only the first file found was used.

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- [DVH] Proper dvh bin-centers (errors were <= bin_width/2)
- [Import] If a plan does not have a BeamSequence or IonBeamSequence (e.g., brachy), a dummy beam is created to
prevent crash if this plan is included in a query.
- [Correlation] None-type values are now removed before correlation calculation and any patient removed from this
calculation is displayed in an error window.

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- [Import] Using rapidfuzz for name prediction (for MIT licensing)
- [Import] Fix for None-Type error with roi_type query during import
- [Export] PNG support for figure export
- [Export] Bundle PhantomJS in executables or load from ~/Apps/dvh_analytics
- [Plots] Grid line customization (color, thickness, alpha)
- [Misc] Store last positions of certain windows (i.e., UserSettings, ExportFigure)
- [Misc] Optionally auto-backup SQLite DB after successful import (enable this in Database Administrator)
or manually backup database in the menu Data -> Backup SQLite DB