ODPSH-152: autofill file format on change

ckanext/odsh/fanstatic/odsh_guessformat.js

ckanext/odsh/fanstatic/odsh_image-upload.js

ckanext/odsh/helpers.py

ckanext/odsh/plugin.py

ckanext/odsh/public/odsh.css

ckanext/odsh/templates/ajax_snippets/fileformat.html

ckanext/odsh/templates/macros/form.html

ckanext/odsh/templates/package/snippets/resource_form.html