Changed 'show solution' button to a 'check' button, to represent the functionality of the button.
Changed icon of check button to check icon.
Changed default value of check button to 'check'.
Changed semantics label and default to correspond with the changes.
Changed enable retry and show solution names.
oppg885
Merge branch 'check-insteadof-showsol' of https://github.com/h5p/h5p-drag-question

Conflicts:
	js/dragquestion.js
Renamed an invalid css class.
Always add buttons and keep them hidden/shown instead.
Revert master. Commited to wrong branch.
Merge branch 'master' of github.com:h5p/h5p-drag-question
Merge branch 'master' into show-score