Configuration for Stasis threadpool

The appropriate settings for the Stasis threadpool is very system
specific, depending upon both workload and system configuration.

This patch adds a stasis.conf file which can be used to configure the
key attributes of the threadpool for the Stasis message bus.

(closes issue ASTERISK-21280)
Review: https://reviewboard.asterisk.org/r/2651/


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@393542 f38db490-d61c-443f-a65b-d21fe96a405b
ARI - channel recording support

This patch is the first step in adding recording support to the
Asterisk REST Interface.

Recordings are stored in /var/spool/recording. Since recordings may be
destructive (overwriting existing files), the API rejects attempts to
escape the recording directory (avoiding issues if someone attempts to
record to ../../lib/sounds/greeting, for example).

(closes issue ASTERISK-21594)
(closes issue ASTERISK-21581)
Review: https://reviewboard.asterisk.org/r/2612/


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@393550 f38db490-d61c-443f-a65b-d21fe96a405b