made single process mode configuration more consistent

* SINGLE_PROCESS_MODE environment variable takes precedence over
  application.yml setting
* SINGLE_PROCESS environment variable takes precedence over
  SINGLE_PROCESS_MODE environment variable to be backward compatible

app/models/app_config.rb

@@ -132,4 +132,8 @@ HELP
     end
     return @@pod_uri
   end
+  
+  def self.single_process_mode?
+    (ENV['SINGLE_PROCESS'] == "true" || ENV['SINGLE_PROCESS_MODE'] == "true" || self[:single_process_mode]) ? true : false
+  end
 end

app/views/js/_websocket_js.haml

@@ -2,7 +2,7 @@
 -#   licensed under the Affero General Public License version 3 or later.  See
 -#   the COPYRIGHT file.
 
--if ENV['SINGLE_PROCESS']
+-if AppConfig.single_process_mode?
   :javascript
     var websocket_enabled = false
 - else

config/initializers/resque.rb

@@ -6,7 +6,7 @@ if !ENV['SINGLE_PROCESS'] && AppConfig[:redis_url]
   Resque.redis = Redis.new(:host => AppConfig[:redis_url], :port => 6379)
 end
 
-if ENV['SINGLE_PROCESS'] || AppConfig.single_process_mode
+if AppConfig.single_process_mode?
   if Rails.env == 'production'
     puts "WARNING: You are running Diaspora in production without Resque workers turned on.  Please don't do this."
   end

script/get_config.rb

@@ -35,9 +35,11 @@ if ARGV.length >= 1
     require 'settingslogic'
     require File.join(Rails.root, 'app', 'models', 'app_config')
     setting_name = setting_name.to_sym
-    if AppConfig[setting_name].nil?
+    if (!AppConfig.respond_to?(setting_name) || AppConfig.send(setting_name).nil?) && AppConfig[setting_name].nil?
       $stderr.puts "Could not find setting #{ARGV[0]} for environment #{Rails.env}."
       Process.exit(1)
+    elsif AppConfig.respond_to?(setting_name)
+      print AppConfig.send(setting_name)
     else
       print AppConfig[setting_name]
     end

script/server

@@ -153,7 +153,7 @@ fi
 
 # Start Diaspora
 
-if [ "$SINGLE_PROCESS" != "true" ]; then
+if [ "$(./script/get_config.rb 'single_process_mode?')" != "true" ]; then
     redis_config
     redis-server config/redis.conf &>log/redis-console.log &