Consider `clear` command

[beckyjackson]

The clear command should take a sheet title and a special keyword (e.g., data-validation or something like that). Then, it will clear all "applied" attributes from the sheet. I think the keywords we want to support are:

• formats
• data-validation (or rules?)
• notes

For example: cogs clear [keyword] -t [sheet-title] or alternatively cogs clear -t [sheet-title] -k [keyword]. I'm not sure which makes more sense.

Let me know if I missed anything.

[jamesaoverton]

We could overload cogs apply with this functionality, but I like a distinct cogs clear better. There should also be an "all" keyword. And it should be possible to clear all sheets.