Give all of the plugins long names

[Masterchef365]

Plugins in general should have long, descriptive names in Cargo.toml; this is already laid out in the book.

For the example plugins, maybe just prefixing with "cimvr_example_".
This helps avoid name collisions.

TODO: Append the semver major number to the pkg_namespace!() macro? Can be retrieved via macros from the stdlib (env!()).