Massive restructure of plugin API

plug-api/lib/dates.ts

@@ -0,0 +1,11 @@
+export function niceDate(d: Date): string {
+  function pad(n: number) {
+    let s = String(n);
+    if (s.length === 1) {
+      s = "0" + s;
+    }
+    return s;
+  }
+
+  return d.getFullYear() + "-" + pad(d.getMonth() + 1) + "-" + pad(d.getDate());
+}