Server: Add basic black-box tests

Aimed mainly at web method invocation (similar to warden_curl_test.sh
from warden_client) and some command line interface commands.

warden_server/README.test

++----------------------------------+
+| Warden3 Server Test Suite README |
++----------------------------------+
+
+Content
+
+  A. Introduction
+  B. Compatibility
+  C. Dependencies
+  D. Usage
+
+-------------------------------------------------------------------------------
+A. Introduction
+
+The Warden Server Test Suite is a collection of high-level functional tests
+(black-box testing), covering the most important interfaces of the Warden
+Server.
+
+-------------------------------------------------------------------------------
+B. Compatibility
+
+* The test suite, just like the Warden Server, is compatible with both Python2
+  (tested on 2.7) and Python3 (tested on 3.6).
+* Just like Warden Server, the test suite requires a local MySQL installation.
+* It is safe to run the test suite on a production system. For testing,
+  a database distinct from the default production one is used. Also, the user
+  account used for accessing the testing database is set for local login only.
+  To be extra safe, make sure not to name the production database `w3test`.
+
+-------------------------------------------------------------------------------
+C. Dependencies
+
+In addition to the regular Warden Server dependencies, package `unittest2` is
+required to run the test suite. It can be installed by running:
+	pip install unittest2
+or `pip3 install unittest2` for Python3 version
+	or on Debian:
+apt-get install python-unittest2
+	or alternatively:
+apt-get install python3-unittest2
+for Python3 version.
+
+An optional dependency is a code coverage measurement tool `Coverage.py`,
+which can be installed by:
+	pip install coverage
+or `pip3 install coverage` for Python3 version
+or on Debian:
+	apt-get install python-coverage
+or alternatively:
+	apt-get install python3-coverage
+for Python3 version.
+
+-------------------------------------------------------------------------------
+D. Usage
+
+Before running the tests (for the first time), a DB user with required rights
+must be created. An easy way to do it is:
+	./test_warden_server.py --init
+This will prompt for MySQL root password.
+
+Standard usage for testing:
+	./test_warden_server.py
+
+Advanced usage:
+
+	./test_warden_server.py --help
+	usage: test_warden_server.py [-h] [-i] [-n]
+
+	Warden3 Server Test Suite
+
+	optional arguments:
+	  -h, --help     show this help message and exit
+	  -i, --init     Set up an user with rights to CREATE/DROP the
+			 test database
+	  -n, --nopurge  Skip the database purge after running the tests
+
+
+Option -n (--nopurge) is meant for debugging purposes and test development, it
+keeps the test database around for inspection after running the tests.
+
+-------------------------------------------------------------------------------