Move TemplateField JS code to a Media class

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

mayan/apps/templating/fields.py

@@ -1,6 +1,9 @@
 from __future__ import absolute_import, unicode_literals
 
 from django import forms
+from django.utils.translation import ugettext_lazy as _
+
+import mayan
 
 from .widgets import TemplateWidget
 
@@ -12,3 +15,8 @@ class TemplateField(forms.CharField):
         self.model = kwargs.pop('model')
         self.model_variable = kwargs.pop('model_variable')
         super(TemplateField, self).__init__(*args, **kwargs)
+        self.help_text = _(
+            'The template string to be evaluated. '
+            'Use Django\'s default templating language '
+            '(https://docs.djangoproject.com/en/%(django_version)s/ref/templates/builtins/)'
+        ) % {'django_version': mayan.__django_version__}