Integrate django-autoadmin into the core apps

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/autoadmin/models.py

@@ -0,0 +1,27 @@
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.db import models
+from django.utils.translation import ugettext_lazy as _
+
+from solo.models import SingletonModel
+
+from .managers import AutoAdminSingletonManager
+
+
+class AutoAdminSingleton(SingletonModel):
+    account = models.ForeignKey(
+        blank=True, null=True, on_delete=models.CASCADE,
+        to=settings.AUTH_USER_MODEL, verbose_name=_('Account'),
+    )
+    password = models.CharField(
+        blank=True, max_length=128, null=True, verbose_name=_('Password')
+    )
+    password_hash = models.CharField(
+        blank=True, max_length=128, null=True, verbose_name=_('Password hash')
+    )
+
+    objects = AutoAdminSingletonManager()
+
+    class Meta:
+        verbose_name = verbose_name_plural = _('Autoadmin properties')