Better Patavi error handling

- Show the cause and code of any error
Add exact SWING preferences
Move MACBETH solve test
Add WS support for exact SWING
Properly calculate the results on last page
Merge branch 'develop' of github.com:gertvv/mcda-elicitation-web into develop

* 'develop' of github.com:gertvv/mcda-elicitation-web:
  Optionally enforce strict monotonicity of PVFs

Conflicts:
	R/macbethSolve-test.R
	R/test/macbethSolve-test.R
	R/test/macbethSolve.R
Remove indifference from MACBETH PVF screen

 - not handled by WS
Fix typo in example JSON
Merge pull request #16 from joelkuiper/develop

Exact SWING, remove MACBETH indifference & error handling