[Enhancement] Allow overriding output templates on a per-source basis (#179)

* Added output path override to table and download option builder

* Added output template override to UI

priv/repo/migrations/20240411154245_add_output_template_to_sources.exs

@@ -0,0 +1,9 @@
+defmodule Pinchflat.Repo.Migrations.AddOutputTemplateToSources do
+  use Ecto.Migration
+
+  def change do
+    alter table(:sources) do
+      add :output_path_template_override, :string
+    end
+  end
+end