Use quantum core for update scheduling

Rather than requiring a traditional crontab install, the app now
leverages quantum-core (link below) to schedule the instance update/sync
task every 5 minutes. Some updates as a result:

  - The new job is scheduled at runtime in server.ex.
  - The update.exs script was refactored to be compiled along with the
    rest of the app as instances.ex.
  - Scheduler and Server modules were added for creating and executing
    the new update task
  - All shell scripts were removed, as they are no longer needed

https://github.com/quantum-elixir/quantum-core

lib/farside/server.ex

@@ -0,0 +1,22 @@
+defmodule Farside.Server do
+  use GenServer
+  import Crontab.CronExpression
+
+  def init(init_arg) do
+    {:ok, init_arg}
+  end
+
+  def start_link(arg) do
+    if System.get_env("FARSIDE_TEST") do
+      IO.puts("Skipping sync job setup...")
+    else
+      Farside.Scheduler.new_job()
+      |> Quantum.Job.set_name(:sync)
+      |> Quantum.Job.set_schedule(~e[*/5 * * * *])
+      |> Quantum.Job.set_task(fn -> Farside.Instances.sync end)
+      |> Farside.Scheduler.add_job()
+    end
+
+    GenServer.start_link(__MODULE__, arg)
+  end
+end