refactor: code restructure

1. split frontend and backend
2. simplify supervisor configuration
3. align backend log format with supervisor
4. set nginx worker to 1
5. delete static web pages

image/usr/local/lib/web/backend/config/__init__.py

@@ -0,0 +1,15 @@
+class Default(object):
+    DEBUG = True
+
+
+class Development(Default):
+    PHASE = 'development'
+
+
+class Staging(Default):
+    PHASE = 'staging'
+
+
+class Production(Default):
+    PHASE = 'production'
+    DEBUG = False