Script to migrate indexes to per-release files (#478)

Script to migrate indexes to per-release files (#478)

* Ignore JetBrains IDE config folders and virtualenvs

* s/libhello/li (index subfolder improper name)

* Fix invalid semantic version in some test crates

s/_/-/, turns out only hyphens are allowed in the pre-release portion.

* Script to split crate files into releases

It applies the foreseeable needed transformations: one release per file, one
file for external definitions; dependencies moved to an array; added name and
version keys.

Fix relative paths during migration