Remove log statement
Allow custom Bad Request errors

BugzID: 17352
Reorder clause to reduce diff noise
Use the design doc cache for design requests

This will use cached design docs for all of the various design handlers
like views, shows, lists, and rewrites.
Reduce log level of batch error
Start a dedicated process to manage config changes

Also, restart chttpd only if the setting actually changed.

BugzID: 13179

Conflicts:
	src/chttpd.erl
Monitor attachment fd's in all cases

Of course there are three separate paths to retrieve attachment
bodies, so let's monitor the Fd in all of them.

BugzID: 16492

Conflicts:
	src/chttpd_db.erl
Remove unused UTF-8 function
Expose mem3_sync backlog size