http: Add chanbans.config, python-dotenv dependency

* chanbans.config handles all configuration now
* python-dotenv dependency is added for basic environment-level
  configuration

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

example.env

@@ -0,0 +1,8 @@
+# Thumbnails directory. Defaults to "thumbs"
+#THUMBS_DIR=thumbs
+
+# HTML cache directory. Defaults to "cache"
+#CACHE_DIR=cache
+
+# Domain name of the server
+HTTP_DOMAIN=domain.com