Autoadmin: Incorporate the autoadmin app

Incorporate the external django-autoadmin app as a core app
and convert it into a Mayan app. This change adds the new
settings: "COMMON_AUTOADMIN_EMAIL", "AUTOADMIN_PASSWORD", and
"AUTOADMIN_USERNAME".

Signed-off-by: Roberto Rosario <Roberto.Rosario@mayan-edms.com>

mayan/apps/common/tests/utils.py

@@ -0,0 +1,15 @@
+from contextlib import contextmanager
+import sys
+
+
+class NullFile(object):
+    def write(self, string):
+        """Writes here go nowhere"""
+
+
+@contextmanager
+def mute_stdout():
+    stdout_old = sys.stdout
+    sys.stdout = NullFile()
+    yield
+    sys.stdout = stdout_old