Give SlotKind a property to indicate whether it is a presentation

[codersquid]

SlotKinds represent types of things on a schedule, some of which have presentations attached as content, some of which do not. In the pinax-symposion-project the schedule grid only renders a presentation if the slot.kind.label is 'talk' or 'tutorial', which leads to issues like pydata/conf_site#68

Back when I was working on SciPy 2014, we forked symposion and changed SlotKind to add presentation = models.BooleanField(default=True, help_text="Whether or not this slot is a presentation")

so that we could change the template conditional to {% if slot.kind.presentation %}
from {% if slot.kind.label == "talk" or slot.kind.label == "tutorial" %} (see _grid.html L16)

[miurahr]

👍 lunch and coffee breaks are important schedule slot! It's modification should be merged.