Set default wsgi workers to cpu_count

Change the default value of wsgi workers from 1 to auto.  The new default
value for workers in the proxy, container, account & object wsgi servers will
spawn as many workers per process as you have cpu cores.

This will not be ideal for some configurations, but it's much more likely to
produce a successful out of the box deployment.

Inspect the number of cpu_cores using python's multiprocessing when available.
Multiprocessing was added in python 2.6, but I know I've compiled python
without it before on accident.  The cpu_count method seems to be pretty system
agnostic, but it says it can raise NotImplementedError or sometimes return 0.

Add a new utility method 'config_auto_int_value' to pull an integer out of the
config which has a dynamic default.

 * drive by s/container/proxy/ in proxy-server.conf.5
 * fix misplaced max_clients in *-server.conf-sample
 * update doc/development_saio to force workers = 1

DocImpact

Change-Id: Ifa563d22952c902ab8cbe1d339ba385413c54e95

etc/account-server.conf-sample

@@ -3,13 +3,19 @@
 # bind_port = 6002
 # bind_timeout = 30
 # backlog = 4096
-# workers = 1
 # user = swift
 # swift_dir = /etc/swift
 # devices = /srv/node
 # mount_check = true
 # disable_fallocate = false
 #
+# Use an integer to override the number of pre-forked processes that will
+# accept connections.
+# workers = auto
+#
+# Maximum concurrent requests per worker
+# max_clients = 1024
+#
 # You can specify default log routing here if you want:
 # log_name = swift
 # log_facility = LOG_LOCAL0
@@ -55,7 +61,6 @@ use = egg:swift#account
 # set log_address = /dev/log
 #
 # auto_create_account_prefix = .
-# max_clients = 1024
 #
 # Configure parameter for creating specific server
 # To handle all verbs, including replication verbs, do not specify