Editing Template:Park trail miles

<noinclude>This returns the total mileage of trails assigned to the park page that this template is called on. 

More specifically, for pages with [[:Category:Trail]] and the property [[Property:Park|Park]] set to the page name, it sums the values in property [[Property:Trail distance round trip|Trail distance round trip]] in miles and returns that value.

It should be called in the following format:
<pre>
{{Park trail sum}}
</pre>
Edit the page to see the template text.
</noinclude>
<includeonly>{{#ask: [[Category:Trail]] [[Park::{{PAGENAME}}]]
 | ?Trail distance round trip#mi
 | format=sum
}}</includeonly>