Display asterisk on checkbox widget
Display asterisk on checkbox widget

If the option `mopa_bootstrap.form.checkbox_label` is set at `widget`
when `mopa_bootstrap.form.render_required_asterisk` is `true`, asterisk
is not display, so I add it.

auipga/MopaBootstrapBundle,naitsirch/mopa-bootstrap-bundle,auipga/MopaBootstrapBundle,auipga/MopaBootstrapBundle,naitsirch/mopa-bootstrap-bundle