Add person's name to alt text

Query the owner's name, include it in the API
response, and then display it in the image ALT
text.  This is needed for 508 compliance #127
Add user names to img alt tags

For screenreaders/accessibility and people who can't
view images/photos, we need to include an alt tag that
has the user's / owner's / volunteer's name.

This commit refactors the `addOwnerName` function into
a user utility, and then calls it from project and task
metadata functions.

Update the rendering of tasks to show the alt text.

Finishes what's requested for #127.