Rework configuration process

Dynamically loads `config.json` on startup.

Fixes #167, #284, #449, #486

Change-Id: I9efb1079c0c88e6e0272c5fda734a367aa8f84a3

docker-compose.yml

@@ -1,12 +1,10 @@
-version: "3"
-
 services:
   synapse-admin:
     container_name: synapse-admin
     hostname: synapse-admin
     image: awesometechnologies/synapse-admin:latest
     # build:
-    # context: .
+    #   context: .
 
     # to use the docker-compose as standalone without a local repo clone,
     # replace the context definition with this:
@@ -18,9 +16,6 @@ services:
     #   - NODE_OPTIONS="--max_old_space_size=1024"
     # default is .
     #   - PUBLIC_URL=/synapse-admin
-    # You can use a fixed homeserver, so that the user can no longer
-    # define it himself
-    #   - REACT_APP_SERVER="https://matrix.example.com"
     ports:
       - "8080:80"
     restart: unless-stopped