Add `meta:local_apply/3`

A way to call a function defined in the module being currently meta-expanded
from external module within `?s/`
Improve error messages

For `badfun` error and "general error" `invalid_splice` error
Add `meta:reify()` stub function

With documentation.
Add arity to "meta-function" stub error messages

Since not all stubs have the same arity
Set next release version to "0.1.0"

Due to API changes (extension)