Simplify test runner by adding a new option '--mayan-apps' that

automatically tests all Mayan apps that report to have tests.
Change the app flag that indicates when an app has test
from 'test' to the more explicit 'has_test'.

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

mayan/apps/user_management/apps.py

@@ -37,8 +37,8 @@ def get_users():
 
 class UserManagementApp(MayanAppConfig):
     app_url = 'accounts'
+    has_tests = True
     name = 'user_management'
-    test = True
     verbose_name = _('User management')
 
     def ready(self):