Add NormalizeRecipeName to unify the various ways a recipe can be
referenced - https/http/ssh URLs, SCP-style git@host:path, already-
canonical host/path, and short catalogue names - to a single stable
"host/path" form, preserving any ":version" suffix. Wire it into
recipe.Get and ValidateRecipe so every entry point accepts git URLs, and
add Recipe.ShortName to recover the bare recipe name from a prefixed one.
Linus Gasser
6d9896fc46