Make file upload work.
Remoe unneeded assignment
chore(eve): use 0.4 eve version

close #46
fix(build): make run script stop on error
fix(data): add missing is_empty method to datalayer

was added in eve 0.3
fix(config): make url_prefix and server_name configurable

SD-281
fix(auth): send CORS headers with 401 response
fix(build): remove server name to make it work with nginx
fix(app): fix app code style
SD-302: Add user: test backend, create unit tests, review

Changed fields created, updated, etag to _created, _updated, _etag
fix(tests): update events handling

close #45 #47