[Enhancement] Optionally use the YouTube API for improved fast indexing (#282)

* Started adding youtube API for fast indexing

* Hooked youtube API into fast indexing

* Added youtube_api_key to settings

* Added youtube api key to settings UI

* Added tests

* Refactored the youtube api module

* More refactor

* Changed editing mode name from basic to standard

* [WIP] started on copy changes

* Updated copy

lib/pinchflat_web/controllers/sources/source_html.ex

@@ -15,6 +15,7 @@ defmodule PinchflatWeb.Sources.SourceHTML do
   def friendly_index_frequencies do
     [
       {"Only once when first created", -1},
+      {"30 minutes", 30},
       {"1 Hour", 60},
       {"3 Hours", 3 * 60},
       {"6 Hours", 6 * 60},