Allow to autoload services on every request

Summary: Use a config to set `autoload`, `autoloadweb` or `autoloadcli` as //true//. Will always default to //false//.

Test Plan: Turn autoload on and check the trace to ensure it was loaded from the excpected location.

Reviewers: brooke

Reviewed By: brooke

Maniphest Tasks: T47

Differential Revision: http://phabricator.cubex.io/D12