Partially fixes https://project.math.uzh.ch/issues/3066: Once the hidden class has been remove in order to display the validation message, it won't be re-added upon validation success.

mockup/second.html: Added standard 'Submit'-button on the bottom of the form. This is an alternative against the regular 'Check'-Button on the top right of the form.

Remove validation messages properly, using bootstrap-validator API

AbstractBuildForm.html: more default configs for the editor. Setting size of the editor.
richttexteditor.html: third RTE to show min/max_height.

Gruntfile.js: Copy tinyMCE plugins.

Conflicts:
	Gruntfile.js
	mockup/chart.html