v2.14: more orderly startup of agents

If the agent has no queues, is logged out, missing the account id, etc, don't
start the agent listener and FSM processes. Return ignore in start_link and
instruct the supervisor to shutdown instead.

Removes almost all of the crash reports and makes startup much cleaner
v2.14: make agent login a request/response with callflow
v2.14: fix couchbeam's design_info url
v2.14: fix compactor's wait_for_design_compaction
v2.14: fix logging of http notification
v2.14: fix display of statuses in maintenance
v2.14: filter status query by status name
v2.14: update agent status to ready only when leaving the 'wait' state

also add a logged_in state to differentiate from returning to 'ready' after
calls and pause and such
v2.14: number output
v2.14: add logged_in stat to stats collector
v2.14: add logged_in api
v2.14: differtiate json encoding errors
v2.14: query stats and statuses for agents or an agent
Merge branch 'v2.14'