Update Django template reference URL from Django 1.7 to Django 1.11. Add migratons to update model definitions.

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

mayan/apps/linking/migrations/0007_auto_20180823_2353.py

@@ -0,0 +1,25 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.11 on 2018-08-23 23:53
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('linking', '0006_auto_20180402_0339'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='smartlink',
+            name='dynamic_label',
+            field=models.CharField(blank=True, help_text="Enter a template to render. Use Django's default templating language (https://docs.djangoproject.com/en/1.11/ref/templates/builtins/). The {{ document }} context variable is available.", max_length=96, verbose_name='Dynamic label'),
+        ),
+        migrations.AlterField(
+            model_name='smartlinkcondition',
+            name='expression',
+            field=models.TextField(help_text="Enter a template to render. Use Django's default templating language (https://docs.djangoproject.com/en/1.11/ref/templates/builtins/). The {{ document }} context variable is available.", verbose_name='Expression'),
+        ),
+    ]

mayan/apps/linking/models.py

@@ -23,7 +23,7 @@ class SmartLink(models.Model):
         blank=True, max_length=96, help_text=_(
             'Enter a template to render. '
             'Use Django\'s default templating language '
-            '(https://docs.djangoproject.com/en/1.7/ref/templates/builtins/). '
+            '(https://docs.djangoproject.com/en/1.11/ref/templates/builtins/). '
             'The {{ document }} context variable is available.'
         ), verbose_name=_('Dynamic label')
     )
@@ -122,7 +122,7 @@ class SmartLinkCondition(models.Model):
         help_text=_(
             'Enter a template to render. '
             'Use Django\'s default templating language '
-            '(https://docs.djangoproject.com/en/1.7/ref/templates/builtins/). '
+            '(https://docs.djangoproject.com/en/1.11/ref/templates/builtins/). '
             'The {{ document }} context variable is available.'
         ), verbose_name=_('Expression')
     )