'datasets.py' correctly shows all DB record data; next implement Save
'datasets.py', work on validating Column records
'datasets.py' Column validation, all except for type 'Aggregate'
'datasets.py' Column verification complete; next, Save
'datasets.py', Save working; next Cancel
moved column validation into separate function 'validateColPanel'
rearranged code, more modular
'datasets.py', Cancel Col changes; just tells user to click around. Improve this later
'datasets.py', start on dataset preview grid
'datasets.py'; begin, preview grid changes by tree selection (stopped tracking code_snippets)
begin, show preview for Book
'datasets.py', preview headers show for Book, Sheet
'datasets.py', all preview headers working; next data preview