Advance export

As an advanced user exporting dataset
I want to be able to precisely select the data to export and not associate it to one specific model
So that I can work with my content in a more flexible way that might lead to less exports or more clean data

action: Switch to advance options on export

Detail

• Should be a new tab on the export page

Export Form:

• Fields that should be present on the form to submit 
  • NQXL query
  • Feature fields (if possible, be suggested/typeahead by the schema rest endpoint)
  • Data split (default 80% - 20%)
  • Time frame (if start is defined, we add it to where clause. same with end date. Default is empty.)
  • Dataset naming (its optional)
• Actions
  • Get statistics (another US)
  • Export (will start exporting)

Also, data statistics card:

• Uses same statistics as the current UI
• It is a collapsable card
• when uses clicks get statistics, the card should expand automatically