Enhance the CKAN file uploading UI with the following features:

• Upload multiple files at once
• Drag & Drop files

Minimal supported CKAN version: 2.8.1

• Activate your CKAN virtual environment
• Install the ckanext-file_uploader_ui package into your virtual environment:
  • pip install ckanext-file_uploader_ui
• If you are using xloader to load data into the datastore
  • install this version of xloader (until this PR is merged)
  • pip install -U https://github.com/OriHoch/ckanext-xloader/archive/support-modifying-download-request.zip#egg=ckanext-xloader
• Add file_uploader_ui to the ckan.plugins setting in your CKAN
• Restart CKAN.

Translations are done in Transifex: https://www.transifex.com/the-public-knowledge-workshop/ckanext-file_uploader_ui

Update the .pot file - should be done in case of additional / modified strings in the templates

python setup.py extract_messages

Edit the .pot file and remove core ckan strings (which are there only because of extending core ckan templates)

Upload pot to transifex, translate on transifex

Install Transifex client

./release.sh --update-translations

Test the updated translations and commit the changes