Unstable release SDAPS 1.9.1

This is a new unstable release pulling in a lot of fixes. Please note that it is incompatible to the previous 1.9.0 release as the fixes to the class will result in the survey IDs to become different.

Important changes:

• Fix repetition of questionnaires
• Fixes to make class work with TeXlive 2017-08-08
• Fix build to not install the TeX class in the users home directory
• Fix LaTeX report generation (#108)
• Fixes and tests of CSV import and exporter
• Improve CSV export to include more information about sheets
• Change default style to QR code