Serve utf-8 paths in python 2

Read config file as utf-8; encode '/serve' staticdir config to prevent
mixing of byte/unicode strings in cherrypy code, which would yield
ASCII decoding errors. (#315, #325, #368)
Improve ConfigError verbosity [ci skip
Remove dead code
Fix unicode filename bug in sqlitecache (#315, #333)

When os.listdir returns a bytestring name, make an effort to decode it;
if that fails, skip the file and log the error.