- moved everything that depended on V1 `Reference` into `FileCodebase` namespace, duplicating a lot of code for better or worse.
- pulled these into their own modules:
    - Codebase (types) into `Codebase.Type`; `Codebase` module re-exports them
    - `Codebase.Branch.Merge`,
    - `Codebase.Branch.Names` (Branch shouldn't depend on `Names`)
    - `Codebase.BuiltinAnnotation`
    - `Codebase.Causal.FoldHistory`
    - `Codebase.CodeLookup.Util` (remove `CodeLookup` dependency on `UnisonFile`)
    - `Codebase.DataDeclaration.ConstructorId` trying to use this alias in relevant places
    - `Codebase.Init`
    - `CodebasePath`, the `FilePath` alias.
    - `Lexer.Pos` (because `AnnotatedText`, `Range`, `Parser.Ann` shouldn't depend on the whole lexer)
    - `Names.ResolutionResult` (`Type` shouldn't depend on `Names`)
    - `PrettyPrintEnv.FQN`
    - `PrettyPrintEnv.Names` (pulled out references to `Names` from `PPE`)
    - `PPE.Util` not 100% sure what's happening here
    - `PrettyPrintEnvDecl` pull this data type and supporting functions into separate module
    - `Path.Parse` (`Path` shouldn't depend on the lexer)
    - `Path.Convert`, `Path.Parse` into `Unison.Util.Convert`
    - `Parser.Ann` (`Codebase`, etc. etc. shouldn't depend on `Parser`)
    - `Referent'` (`SyntaxText`/`ColorText` shouldn't depend on `Reference`)
        - `Referent` module re-exports stuff from `Referent'`, hard-coded to `Reference`.
    - removed `SyntaxText.SyntaxText`
    - `TermEdit.Typing` (because `TermEdit` shouldn't depend on the full typechecker)
    - `UnisonFile` / `TypecheckedUnisonFile` (types into `UnisonFile.Type`)
    - `UnisonFile.Env`
    - `UnisonFile.Error`
    - `UnisonFile.Names`
    - `Var.WatchKind`
    - `Var.refNamed`
- Deleted unused `Codebase.Classes` typeclasses wip
- Deleted unused `Unison.Util.Menu`, ancient modal stuff
- Moved `Codebase.makeSelfContained` into `UnisonFile` module, since it deals with `UnisonFile` and not with `Codebase`.
- split up `GitError` into a more codebase-agnostic hierarchy (see `Codebase.Type.GitError`)
- changed `bindNames` to `bindReferences` in some cases; `bindNames` remains in `.Names` compatibility module
- move `Unison.Var.refNamed` into `Unison.Term`
- tweaked GitError to separate obviously codebase-format specific errors from non-obviously-corbase-format-specific errors.
- tweaked `Reflog.Entry` to support anything that's coercible to `Unison.Hash`, but also changed its kind
- removed `DebugBranchHistoryI` input because I didn't want to maintain its implementation
- removed `ShortBranchHash` dependency on `Hash`, and let it work on anything coercible to `Hash`.  P.S./todo This class should be called ShortHash; the existing ShortHash is really a ShortReference!
- removed SyntaxText dependency on Reference
- cleaned up `Path` somewhat
- held off on:
    - move `DD.updateDependencies`
    - splitting up `Path` into the billion different components
        - e.g. `Path` becomes `RelativePath`, `Path'` becomes `Path`, and `Absolute` wraps `RelativePath`
        - `Split` / `Split'` maybe rename to `Path.NonEmpty`?
    - rename `Branch.getPatch` / `.getMaybePatch`
    - split out `Name.Parse`, `Name.Convert`, substitute a lot of specific functions like `Path.hqSplitFromName'` with `Convert.parse`.
- todo:
    - clear unreferenced junk
    - restore:
        - `NameEdit`?
        - `PatternCompat`?

and DebugBranchHistoryI

# Conflicts:
#	parser-typechecker/src/Unison/Codebase.hs
#	parser-typechecker/src/Unison/Codebase/Editor/HandleCommand.hs
#	parser-typechecker/src/Unison/PrettyPrintEnv.hs
#	parser-typechecker/unison/Main.hs
#	unison-core/src/Unison/Names3.hs
#	unison-core/src/Unison/Pattern.hs
#	unison-core/src/Unison/Term.hs
#	unison-core/src/Unison/Type.hs
#	unison-core/src/Unison/Util/Relation.hs
#	unison-core/unison-core1.cabal

and update messages