Change parameter form booleans to sliders

[kvig]

#308 switched the UI checkboxes to sliders. The Parameter forms were untouched due to a more involved process. The starting point for this is ui/forms/tasks.py, specifically TaskParameterForm::get_field_info().

In #308, there were additions to the surrounding <div/>'s as well as the field itself, so take that into consideration as well.