res_pjsip: AMI commands and events.

Created the following AMI commands and corresponding events for res_pjsip:

PJSIPShowEndpoints - Provides a listing of all pjsip endpoints and a few
                     select attributes on each.
  Events:
    EndpointList - for each endpoint a few attributes.
    EndpointlistComplete - after all endpoints have been listed.

PJSIPShowEndpoint - Provides a detail list of attributes for a specified
                    endpoint.
  Events:
    EndpointDetail - attributes on an endpoint.
    AorDetail - raised for each AOR on an endpoint.
    AuthDetail - raised for each associated inbound and outbound auth
    TransportDetail - transport attributes.
    IdentifyDetail - attributes for the identify object associated with
                     the endpoint.
    EndpointDetailComplete - last event raised after all detail events.

PJSIPShowRegistrationsInbound - Provides a detail listing of all inbound
                                registrations.
  Events:
    InboundRegistrationDetail - inbound registration attributes for each
                                registration.
    InboundRegistrationDetailComplete - raised after all detail records have
                                been listed.

PJSIPShowRegistrationsOutbound  - Provides a detail listing of all outbound
                                  registrations.
  Events:
    OutboundRegistrationDetail - outbound registration attributes for each
                                 registration.
    OutboundRegistrationDetailComplete - raised after all detail records
                                 have been listed.

PJSIPShowSubscriptionsInbound - A detail listing of all inbound subscriptions
                                and their attributes.
  Events:
    SubscriptionDetail - on each subscription detailed attributes
    SubscriptionDetailComplete - raised after all detail records have
                                 been listed.

PJSIPShowSubscriptionsOutbound - A detail listing of all outboundbound
                                subscriptions and their attributes.
  Events:
    SubscriptionDetail - on each subscription detailed attributes
    SubscriptionDetailComplete - raised after all detail records have
                                 been listed.

(issue ASTERISK-22609)
Reported by: Matt Jordan
Review: https://reviewboard.asterisk.org/r/2959/
........

Merged revisions 403131 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@403133 65c4cc65-6c06-0410-ace0-fbb531ad65f3