Support for publishing of crates in subdirectories of repositories (#939)

Support for publishing of crates in subdirectories of repositories (#939)

* Added require information to Origins

* Unique folder name for monorepos

* Use subdir all around, but for publishing

* Alire.Publish: detect and publish nested crates

* Alire.Roots: Properly deploy/use nested crates

* Test for basic publishing and using of monorepo

* Test for nesting beyond the top level

* Test no subdir accepted for non-repo origins

* user-changes.md: new monorepo feature

* Updates to various documentations

* Create info file for monorepo releases

This is an empty file in the dependencies folder that helps curious users to
understand where a particular release is coming from. For example:

dependencies
 +-- monorepo_adef1234
      +-- mycrate
 +-- mycrate_1.0.0_in_monorepo_adef1234

* Self-review fixes

* Fixes for Windows

Windows may return paths with either long or short names which complicate a bit
comparing two directories as we do to detect nested crates. To us, the problem
esteems from git returning different names than the Ada std lib.

* Alire.Releases: fix obsolete header box

Co-authored-by: Jesper Quorning <jesper.quorning@gmail.com>
* Test using crates from different monorepo commits

Co-authored-by: Jesper Quorning <jesper.quorning@gmail.com>