Change "reusability" to "type" for invites

- This makes the choice much clearer
- Allows for less generic terms in the table
- Future extensibility \o/

snikket_web/templates/library.j2

@@ -107,3 +107,11 @@
 <em>{% trans %}deleted{% endtrans %}</em>
 {%- endif -%}
 {% endmacro %}
+
+{%- macro invite_type_name(invite_info, caller=None) -%}
+{%- if invite_info.reusable -%}
+{% trans %}Group{% endtrans %}
+{%- else -%}
+{% trans %}Individual{% endtrans %}
+{%- endif -%}
+{%- endmacro -%}