* Polish rewrite docs
* Add documentation comments, add missing evaluator options
* Add ability to set HTTP builder in ConfigEvaluatorBuilder
* Add ability to set rewrites in executor API
This adds a new feature, which allows Pkl to read resources and modules from external processes.
Follows the design laid out in SPICE-0009.
Also, this moves most of the messaging API into pkl-core
* Add `--proxy` and `--no-proxy` CLI flags
* Add property `http` to `pkl:settings`
* Move `EvaluatorSettings` from `pkl:Project` to its own module and add property `http`
* Add support for proxying in server mode, and through Gradle
* Add `setProxy()` to `HttpClient`
* Add documentation