Fix missing enctype="multipart/form-data" when needed

- add app example.files with tests, based on example2.
- add check in base update template which checks if
  form.is_multitype and adds the encoding for it
- update gitignore to ignore the uploaded media folder
- add test to blog to ensure that the create form is not
  multipart encoded
Merge pull request #372 from yarbelk/fix_multipart

Fix missing enctype="multipart/form-data" when needed