zeroconf: Move all logging to debug level
http: Catch socket errors when handling websockets (fixes #571)
(cherry picked from commit 94fe38ff09d048153585713180d317378db1f6cc)
docs: Update changelog
local: Make clear command mesages more clear

(cherry picked from commit 812f018d5923829cad0a7bcfcea3cb428bf95f18)
local: Fix typo

(cherry picked from commit 884c1b9803d024f1d1615ad10ce4bdc30e9d8e41)
local: Use print() function

(cherry picked from commit d0a305a8e2208d1188c4013328a64d5d7f17de9c)
config: Make keyring log messages explain more

...as a lot of users see debug-level errors from the keyring code and think
they explain some larger issue. These are currently *always* red herrings as
there is no command for setting configuration values in the keyring yet.

Fixes #681
config/ext: Automatically disable extensions with bad config

Ensures config errors on extensions don't block mopidy startup. Also improves
error messages for config problems.

(cherry picked from commit 684bfcf301c7f945308894ca54bc02be627d4d16)
docs: Update changelog
Bump version number to 0.18.2
docs: Update changelog for v0.18.2
Release v0.18.2
Merge branch 'master' into develop

Conflicts:
	docs/changelog.rst