cargo-psibase package command improvements

[James-Mart]

I propose the commands:

• cargo psibase package new package_name - generates a skeleton package named packaged_name
  • --description=example
  • --service=serv1
  • --server=serv2
  • --plugins=plugin1

Creates the package format demoed in ./rust/test_package. It should create the same basic service for each generated service, the same basic plugin for each generated plugin. To generate plugins, we can rely on the user already having cargo component installed, so we can just run cargo component new --lib --namespace serv1 plugin to generate the plugin for serv1 in a subdirectory called plugin.

[James-Mart]

CC @swatanabe thoughts?