docs: Add links to blog posts on commit messages
docs: Remove extensiondev draft warning
docs: Remove link to removed document
docs: Add mopidy.ext to API docs
docs: Minor updates to extensiondev docs
docs: Remove extension support implementation plan
docs: Add note about extension's API usage
docs: Link from ext API to extensiondev
docs: Note about logging in extensions
docs: Add TODOs for documenting command line options
Merge branch 'develop' into feature/reshuffle-config

Conflicts:
	mopidy/ext.py