Add gen-config tool

This patch adds gen-config tool which wraps oslo-config-generator.
It also moves README-higgins.conf.txt and
higgins-config-generator.conf files from etc/higgins to tools
directory so etc/higgins will only be used to maintain configuration
files of Higgins service.

Change-Id: I53cc5aeba6001b147c7cf6ffba33056470646f0f

etc/higgins/README-higgins.conf.txt

@@ -1,12 +0,0 @@
-To generate the sample higgins.conf file, run the following
-command from the top level of the higgins directory:
-
-tox -egenconfig
-
-Or you can generate the sample higgins.conf file in global
-environment, run the following command from the top level
-of the higgins directory:
-
-pip install oslo.config
-oslo-config-generator --config-file \
-                etc/higgins/higgins-config-generator.conf

tools/README-higgins.conf.txt

@@ -0,0 +1,12 @@
+To generate the sample higgins.conf file, run gen-config tools
+from the top level of the higgins directory:
+
+tools/gen-config
+
+Or run the following command from the top level of the
+higgins directory:
+
+tox -egenconfig
+
+Generated sample configuration file will be put into etc/higgins/
+directory.

tools/gen-config

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+oslo-config-generator --config-file=tools/higgins-config-generator.conf

tox.ini

@@ -91,5 +91,6 @@ install_command = pip install -U --force-reinstall {opts} {packages}
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:genconfig]
+envdir = {toxworkdir}/venv
 commands =
-    oslo-config-generator --config-file etc/higgins/higgins-config-generator.conf
+  {toxinidir}/tools/gen-config