Adds QR Code Invitation for in Person Elections

See merge request !48

Adresses issue #30 and #45

* version 1.0.5
* close buttons are now btn-secondary which makes them grey instead of
white

Default publish

See merge request !47

UI Improvements

See merge request !46

* Unify submit buttons to have submit and cancel button
* Cancel is always like a back button and actually just a link
* Change Button color to blue and grey instead of green and red

The fronted now correctly shows when no elections exist in both
management and voter frontend

Session Title Changeable

See merge request !45

* when creating new election
* in session settings

Fixes issue #38

Closes #38

See merge request !44

Fixes issue #44

Closes #44

See merge request !43

Add Selectors

Closes #31

See merge request !42

- result_unpublished -> result_published
- disable_abstention -> enable_abstention

Fixes image paths in the help page