Define API for obtaining geographic bounding box coordinates

[peterwtux]

We use /boundaries.xml to give clients a bounding box for our jurisdiction. This allows them to quickly identify points that are clearly unacceptable to us, and for which we won't accept service requests. Sample output:

<boundaries>
<bottom>37.123</bottom>
<left>-79.001</left>
<top>38.456</top>
<right>-78.678</right>
</boundaries>