add all modules, better gradle setup, and elixir for server

plt-server/test/plt_server_test.exs

@@ -0,0 +1,8 @@
+defmodule PltServerTest do
+  use ExUnit.Case
+  doctest PltServer
+
+  test "greets the world" do
+    assert PltServer.hello() == :world
+  end
+end

plt-server/test/test_helper.exs

@@ -0,0 +1 @@
+ExUnit.start()