New `help -dump-cells-json <file>` to dump cells list.
Add 'group' field to SimHelper class/struct with defaults to gate_other and word_other depending on source (simcells or simlib).
Add 'unary' group to unary operator cells for testing (based on internal cell library docs page).
- Drop `cell_code` and instead map code lookups to the `cell_help` dict.
- Add helper functions to struct for checking and getting the right cell.
- Add `CellType` for cell to `write_cell_rst` function declaration in
preparation for use in future.
- Iterate over `yosys_celltypes.cell_types` when exporting cell rst files,
reporting errors for any cells defined in `cell_types` but not
`cell_help_messages`.
Since `simcells.v` uses consistent formatting we can handle it specifically to help tidy up sphinx warnings about the truth tables, and instead chuck them in a code block which when printing to rst.
Also has the side effect that rst code blocks can be added manually with `//- ::` followed by a blank line.
Include Source file and line number in SimHelper struct, and use it for verilog code caption in rst dump.
Also reformat python string conversion to iterate over a list of fields instead of repeating code for each.
Allows for more expressive code when constructing help messages for cells.
Will also move extra logic in parsing help strings into the initial python parse instead of doing it in the C++ at export time.