Update ACL app to compy with MERC 5 and 6

Update the entire with keyword arguments. Update the views
to comply with MERC 6 by returning error 404 on access
failure. API are untouched. Add icon to the ACL delete
button. Add additional view tests. Use the new filtered
choice form to display a select2 enabled role selection
widget. Update the ACL creation view to not redirect to an
existing ACL in case of duplication but to instead stop
and display an error with a suggestion to the user
to instead edit the existing ACL.

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

mayan/apps/acls/forms.py

@@ -0,0 +1,13 @@
+from __future__ import unicode_literals
+
+from django import forms
+
+from mayan.apps.common.forms import FilteredSelectionForm
+
+from .models import AccessControlList
+
+
+class ACLCreateForm(FilteredSelectionForm, forms.ModelForm):
+    class Meta:
+        fields = ('role',)
+        model = AccessControlList