Standardize metainfo property generation, setting, and skipping

I'm noticing a common pattern with metainfo property flags to `imdl torrent create`. Many flags are concerned with setting a metainfo property (`--source`), avoiding setting a property, (`--no-creation-date`), or similar.

I'm considering changing argument handling to deal with these operations in a more uniform way:

- A `--with` flag, to include a property whose value has a reasonable default: `--with creation-date`
- A `--without` flag, to not include a property that would have been included by default: `--without created-by`
- A `--set flag`, to set a property to a particular value: `--set source hello`

Many of the flags to `imdl torrent create` could be removed in favor of these three flags. A huge bonus to this would be that these same flags could be reused for an eventual `imdl torrent edit` command, to add, remove, and set properties on existing torrents.

Start at the `imdl torrent create` argument handling and inventory the existing metainfo property flags, their defaults, and skip behavior. Compare that inventory with the proposed `--with`, `--without`, and `--set` interface; done requires an agreed design and consistent handling, but the issue names no files or tests.

Written by the indexing model from the issue text.