Misc indexing improvements (#99)

* increased file follower timeout to 10 minutes

* Removed unique index across a source's collection and its media profile

* Ensure source gets updating during slow indexing

lib/pinchflat/slow_indexing/file_follower_server.ex

@@ -9,7 +9,7 @@ defmodule Pinchflat.SlowIndexing.FileFollowerServer do
   require Logger
 
   @poll_interval_ms Application.compile_env(:pinchflat, :file_watcher_poll_interval)
-  @activity_timeout_ms 60_000
+  @activity_timeout_ms 600_000
 
   # Client API
   @doc """