Output polyglot XHTML rather than HTML

No need to lose the benefits of XML when we know that the document can't
be malformed.  Output as HTML-compatible XHTML.

Note:  We're already using the XHTML doctype rather than the HTML one.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
Use XHTML 1.0 Strict DOCTYPE

We don't need any of the features present in transitional XHTML, so
declare that we conform to strict.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
Replace <tt> with <code>

<tt> has been removed in HTML5.  Replace it with <code>.  This is the
clear choice for the XPath information (since it is clearly computer
code).  It's arguable whether the constant values are really code or
something else, but <code> is close enough for me.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
Fix header levels

The header level-based outline of the generated page didn't reflect its
structure due to headers at the wrong level.  Correct these.  Keep style
unchanged (except for some small size changes).

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
Use <var> instead of <strong> for parameters

By using <var> we can convey the semantics for why the parameters are
displayed with a bold font (because they are input variables) in
addition to making them visually bold.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
Include resource path in title

Previously the stylesheet would use either the resource doc title or the
resource path (with parameters appended).  Although this gives the WADL
author more flexibility for exactly what is in the title, it leads to
annoying duplication if the author prefers to have the path in the
title.  Therefore, add the path to the title automatically.

Note:  This is a style choice and may not be generally preferable.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
Include doc title in method header

If the user has included a title for the <doc> child of a <method>,
include that title in the header for that method.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
STYLE: Add margin between method blocks

When the header of a method block bumps up against the end of the
previous method block it gets difficult to read (for me).  Add a bit of
extra space between method blocks.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>