Fix flask-admin for CIText type

The CIText type is not known by Flask-Admin and was not rendered.
A custom model converter is required.

See https://github.com/flask-admin/flask-admin/issues/1196

app/admin/views.py

@@ -9,13 +9,24 @@ This module customizes the admin views.
 :license: BSD 2-Clause, see LICENSE for more details.
 
 """
-from wtforms import validators
+from wtforms import validators, fields
 from flask_admin.contrib import sqla
+from flask_admin.model.form import converts
 from flask_login import current_user
 from ..models import Item, User, Group, ICS_ID_RE
 
 
+# Add custom model converter for CIText type
+# See https://github.com/flask-admin/flask-admin/issues/1196
+class AppAdminModelConverter(sqla.form.AdminModelConverter):
+
+    @converts('CIText')
+    def conv_CIText(self, field_args, **extra):
+        return fields.TextAreaField(**field_args)
+
+
 class AdminModelView(sqla.ModelView):
+    model_form_converter = AppAdminModelConverter
 
     def is_accessible(self):
         return current_user.is_authenticated and current_user.is_admin