global: make ready for self hosting

This exposes a few more env vars for configuration &
bypasses the Subscription backend
so each user is Pro by default. This is required because there won't be
any mechanism for the user to upgrade. We'll also have to disable a few
things on the client side to avoid confusion.

Notesnook.API/Services/S3Service.cs

@@ -19,6 +19,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Net.Http;
 using System.Text.RegularExpressions;
 using System.Threading.Tasks;
@@ -41,7 +42,6 @@ namespace Notesnook.API.Services
 
         public S3Service()
         {
-
             var config = new AmazonS3Config
             {
 #if DEBUG