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.

Remove validation messages properly, using bootstrap-validator API

Preview commit for field validation using bootstrap-validator. Do a `make boostrap && grunt` after merge

Form.js: Textarea also get input and paste event listener in order to fire upon changes immediately.

 * use anonymous functions for ajax error displays
 * expect response from server to file upload to have `status` and `message` attributes
 * replaced occurrences of `QfqNS` by `n` in order to support different namespace names.

qfq-bs.css.less: Tweaked less. Added new class for spinner. Changed display type of input[type=file].
FileUpload.js: every callback will be called with the originating file input element as first parameter.
QfqForm.js: Add spinner on upload.

BSTabs.js, PageState.js, Form.js: done.
Alert.js: first draw, layout not of alerts not proper yet.
Added jasmine tests.