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/document_signatures/apps.py

@@ -46,8 +46,8 @@ logger = logging.getLogger(__name__)
 class DocumentSignaturesApp(MayanAppConfig):
     app_namespace = 'signatures'
     app_url = 'signatures'
+    has_tests = True
     name = 'document_signatures'
-    test = True
     verbose_name = _('Document signatures')
 
     def ready(self):