#16 support browser-supported mime types

[Willie Northway]

Each browser maintains it's own list of supported mime
types. We should be able to tap into that to decide
whether or not to allow the user to "view" the file or not.

For example, one can see the list of supported mime
types with this code:

<script>
<!--
for ( var i = 0; i < navigator.mimeTypes.length; i++ ) {
document.write(
'<p>'+navigator.mimeTypes[i].type+'</p>' );
}
-->
</script>