* APIv2 Rewrite first draft
Add WIP JSON RPC handler for APIOwner via proc-macro generated API, using the easy-jsonrpc crate.
* patch dependency on grin core to get serializable errors
* doctest ownerapi, update easyjsonrpc version
* begin impl ForeignApi
* https://github.com/mimblewimble/grin/pull/2659 is merged, switch from using forked repo
* write jsonrpc doctests for ForeignApi