Add new API library for data importing (Gephi and CSV)
Data import: use POST
Data import: Move from simplejson to ujson. Better performance.
Data import: Add JSON mimetype. Some refactoring.
Data import: ensure that is an AJAX request
Data import: rename file
Data import: first steps for the new UI
Data import: add drag and drop support
Data import: change function parameters in loadGEXF and loadCSV

Now they receive as parameters a FileList object.
Data import: last steps for the new UI
Data import: change fading duration
Data import: reject promises if nodes can not be loaded
Data import: show user message if nodes can not be loaded
Data import: check CSV files mimetype
Data import: refactoring (DRY)
Data import: disable radio buttons after data loading
Data import: refactoring (DRY)
Data import: progress bar and some fixes
Data import: styling progress bar
Data import: exclude forbidden property names