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Fixed precision bug for negative numbers
Mouse_wheel now works for mac
Removed xlrd dep
Column name length and max cell width in adjustColumnWidths
Can now use different datetime formats
Changed header color variable names
Can set row header color in prefs
Index header uses row header color
Fix to prevent editing when in filtered mode
float32 type recognised, works for precision
No longer allows non dtype edits unless column type is changed first
Show git version in help dialog
Page up and page down now works
ctrl+ and ctrl- for zooming table
Fix to move_to_selection to redraw table
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