Restructure project

We previously didn't really had any structure in our project apart
from creating a new folder for each package in our project root.
Now that we have accumulated some packages, we use the well-known
Golang project layout in order to clearly communicate our intent
with packages. See https://github.com/golang-standards/project-layout

api/websocket.schema.json

@@ -0,0 +1,44 @@
+{
+  "$schema": "http://json-schema.org/schema#",
+  "title": "event",
+  "type": "object",
+  "oneOf": [
+    {
+      "properties": {
+        "type": {
+          "const": "exit",
+          "required": true
+        },
+        "data": {
+          "type": "integer",
+          "required": true,
+          "minimum": 0,
+          "maximum": 255
+        }
+      },
+      "additionalProperties": false
+    },
+    {
+      "properties": {
+        "type": {
+          "enum": [ "stdout", "stderr", "error" ],
+          "required": true
+        },
+        "data": {
+          "type": "string",
+          "required": true
+        }
+      },
+      "additionalProperties": false
+    },
+    {
+      "properties": {
+        "type": {
+          "enum": [ "start", "timeout" ],
+          "required": true
+        }
+      },
+      "additionalProperties": false
+    }
+  ]
+}