Fix conversion of references to commits (#761)

Fix conversion of references to commits (#761)

* Completed Roots.Editable commands for removal

* Completed Alr.Commands.Pin

* Reinstated all `alr pin` functionality

* Reinstated remaining disabled pin tests

* Reinstated remaining disabled tests

* Testsuite: fix platform-independent path on Windows

* Implement pin commands in alr driver

* Testsuite: Implement with command in alr driver

* Testsuite: equivalence between manual and cmd-line

* Fix git folder deletion on Windows

* Fix reference to commit mode