server/general: ditch falcon for in-house WSGI app

For quite some time, I hated Falcon's class maps approach that caused
more chaos than good for Szurubooru. I've taken a look at the other
frameworks (hug, flask, etc) again, but they all looked too
bloated/over-engineered. I decided to just talk to WSGI myself.

Regex-based routing may not be the fastest in the world, but I'm fine
with response time of 10 ms for cached /posts.

server/.pylintrc

@@ -1,6 +1,7 @@
 [basic]
 function-rgx=^_?[a-z_][a-z0-9_]{2,}$|^test_
 method-rgx=^[a-z_][a-z0-9_]{2,}$|^test_
+const-rgx=^[A-Z_]+$|^_[a-zA-Z_]*$
 good-names=ex,_,logger
 
 [variables]