Constant-based TypeString hierarchy system

It's becoming increasingly clear I need to build a constant-based TypeString hierarchy, such that a bundle.js or es5.js is a type of JS file, and thus gets proper mimetypes, etc, while remaining more specific.

This should somehow get hooked into the resolver ConversionGraph AND the Detection / sanity check system

Reqs:

- Modifications should be able to be made at LOW LEVELS while preserving HIGH LEVEL concepts. For example, `git-tree.json` is a form of json and thus can be converted to, say, yaml, HOWEVER, it will remain a `git-tree.yml` then. JSON -> YAML should not know about `git-tree`, and `git-tree` should not know about yaml

- Another example: thumb.png is a PNG, and can be convered into thumb.jpg while preserving its characteristiscs

- Also keep track of lossy vs nonlossy conversions

- Maybe "format" vs. "context"...?

```
builtin/converters/git.py

58 class InlineJsVariable(converter.Converter):
59 inputs = [
60 'git-tree.html',
61 # 'HTML',
62 # TODO: once there is a type hierarchy, then this should handle any
63 # sub-type of HTML
64 ]

```

Start by reading builtin/converters/git.py around InlineJsVariable and then trace the resolver ConversionGraph and Detection/sanity check system mentioned in the issue. Define how constant-based TypeString subtypes preserve higher-level concepts across conversions, including lossy versus nonlossy behavior. Done means subtype conversions such as git-tree.json to YAML and PNG to JPG retain their specific characteristics while generic conversions remain independent of those subtypes.

Written by the indexing model from the issue text.