Backlog of features to implement (in no particular order):
- Selected cells in sheet (worksheet->sheetViews->sheetView->selection->sqref). Should wait for Group.
- Support rich text (in cell values and shared strings)
- Sheet: Rename, delete. Will require manipulating/clearing formulas.
- When clearing a shared formula ref cell, we should move the shared formula ref to another.
- Returning a shared formula in a not ref cell returns "SHARED". We should return a translated formula.
- ColumnRange, RowRange, Group
- Support sheet, row, and column styles. That will require iterating over all contained styles and updating.
- Conditional formatting
- Print settings
- Formula parsing
- Charts
- Cell comments. Will require rich text parsing. A comments relationship is creating in the sheet rels file that points to a commentsN.xml file.
- Cell protection
- Copy style
- Built-in styles
- Named styles
- Insert images
- Frozen rows/columns
- Create defined name
- Enum of standard number formats?
- Drawings
- Array formulas - May want to introduce a new Formula class.