Add disclaimer about PII/PHI to data upload page

[JPReceveur]

On the data upload tool, can we add a required checkbox for users to click to assert that their data does not contain any personally identifiable information or protected health information?

e.g. on the upload dataset page a checkbox at the bottom that states 'The uploaded data meets submission requirements and does not contain any personally identifiable information or protected health information (more information)'

[jorvis]

SQL updated needed in all dbs:

ALTER TABLE dataset
  ADD COLUMN user_pii_affirmed TINYINT DEFAULT 0
  AFTER annotation_release;

[jorvis]

Code merged into devel from issue-1193-data-upload-disclaimer branch.