Add a fetch seed_type

[jkomoros]

Allows fetching from a remote origin. This is the primary way to get things in and out. It's also dangerous!

Fetches from seeds from local seed packets should be allowed, but the first time a remote seed fetches from a given URL, the user should get a chance to confirm (with a 'allow from now on'). The profile should store which seed packet locations the user has allowed to remember which ones need a confirmation.

The fetch should allow configuring subsubset of fetch parameters.

Having an ability to store a secret store for a seed packet that only it can reference would be useful for API keys for fetch that the library isn't aware of for its own use.

property seed type should work for dotted gets so it's possible to traverse into them

• Add a fetch for remote URLs
• Headers
• Body
• (other parameters)
• format (json (default), string)
• Add a fetch for local / relative URLs (if it needs to be supported differently)
• Add disallow_fetch protected property
• An option to not throw for http errors and instead pass back a string
• When a seed from a remote packet initiates a fetch, ask the first time.
• Filesystem profile should persist locations