Interop chain start strategies (#479)

* Implement more flexible beacon chain genesis

* Fix compile issues from rebase on master

* Rename CLI flag

* Adds initial documentation for TOML files

* Update docs readme

* Add first version of cli_util

* Dont write cache fields in serde

* Tidy cli_util

* Add code to load genesis YAML file

* Move serde_utils out of tests in `types`

* Update logging text

* Fix serde YAML for Fork

* Make yaml hex decoding more strict

* Update deterministic key generate for interop

* Set deposit count on testing genesis state

* Make some fixes for deposit count

* Remove code fragements

* Large restructure of docs

* Tidy docs

* Fix readme link

* Add interop docs

* Tidy README

docs/README.md

@@ -0,0 +1,69 @@
+# Lighthouse Documentation
+
+_Lighthouse is a work-in-progress. Instructions are provided for running the
+client, however these instructions are designed for developers and researchers
+working on the project. We do not (yet) provide user-facing functionality._
+
+## Introduction
+
+- [Overview of Ethereum 2.0](serenity.md)
+- [Development Environment Setup](env.md)
+
+For client implementers looking to inter-op, see the [Inter-Op
+Docs](interop.md).
+
+## Command-line Interface
+
+With the [development environment](env.md) configured, run `cargo build --all
+--release` (this can take several minutes on the first build). Then,
+navigate to the `target/release/` directory and read the CLI documentation
+using:
+
+```
+$ ./beacon_node -h
+```
+
+The main [`README.md`](../README.md#simple-local-testnet) provides instructions
+for running a small, local testnet.
+
+## REST API
+
+The beacon node provides a RESTful HTTP API which serves information about the
+Beacon Chain, the P2P network and more.
+
+This API is documented in the [`rest_oapi.yaml`](rest_oapi.yaml) Swagger YAML
+file. There's an interactive version hosted on
+[SwaggerHub](https://app.swaggerhub.com/apis/spble/lighthouse_rest_api/0.1.0).
+
+The implementation of the Swagger API in Lighthouse is incomplete, we do not
+(yet) guarantee that all routes are implemented.
+
+## Configuration Files
+
+Lighthouse uses [TOML](https://github.com/toml-lang/toml) files for
+configuration. The following binaries use the following config files (they are
+generated from defaults if they don't already exist):
+
+- [Beacon Node](/beacon_node)
+	- [`~/.lighthouse/beacon_node.toml`](#beacon-nodetoml): the primary
+		configuration file for a beacon node.
+	- `~/.lighthouse/eth2-spec.toml`: defines chain-specific "constants" that
+		define an Ethereum 2.0 network.
+- [Validator Client](/validator_client)
+	- `~/.lighthouse/validator_client.toml`: the primary configuration file for
+		a validator client.
+	- `~/.lighthouse/eth2-spec.toml`: defines chain-specific "constants" that
+		define an Ethereum 2.0 network.
+
+_Note: default directories are shown, CLI flags can be used to override these
+defaults._
+
+#### `beacon-node.toml`
+
+A TOML configuration file that defines the behaviour of the beacon node
+runtime.
+
+- Located in the `datadir` (default `~/.lighthouse`) as `beacon-node.toml`.
+- Created from defaults if not present.
+
+See the [example](config_examples/beacon-node.toml) for more information.