Validation and rendering fixes for HTML5 and XHTML

removed extra <section/>
added missing tr tags
close <dd> tags
close <meta>, <img>, and <br> tags
renamed duplicate id literals-to-identifiers to
mapping-from-DDI-XML-to-DDI-RDF
escaped < and > in <pre> blocks
escape &&
in html5, <ul> and <h4> can not be nested in <p>. switch to <div>
added alt tags