Add client support for custom configuration file paths

This change adds client support for setting custom configuration
file paths, allowing users and developers to place their settings
file wherever they want. All client demo scripts have been updated
to support a '-s' flag that can be used to set the configuration
file for the demo. Client unit tests have also been updated to
include this change.

kmip/core/config_helper.py

@@ -45,15 +45,20 @@ class ConfigHelper(object):
     # Timeout measured in seconds
     DEFAULT_TIMEOUT = 30
 
-    def __init__(self):
+    def __init__(self, path=None):
         self.logger = logging.getLogger(__name__)
 
         self.conf = SafeConfigParser()
-        if self.conf.read(CONFIG_FILE):
-            self.logger.debug("Using config file at {0}".format(CONFIG_FILE))
+
+        filenames = path
+        if not path:
+            filenames = CONFIG_FILE
+
+        if self.conf.read(filenames):
+            self.logger.debug("Using config file at {0}".format(filenames))
         else:
             self.logger.warning(
-                "Config file {0} not found".format(CONFIG_FILE))
+                "Config file {0} not found".format(filenames))
 
     def get_valid_value(self, direct_value, config_section,
                         config_option_name, default_value):