ENH: begin reworking doxygen to use xhtml/css and new OpenCFD look

- drop old table-based formatting in favour of div.
- use single css with @import to minimize the impact of style changes
  on the html documents themselves.
- separate css/ directory
- locate css graphic elements inside the css/ directory for easier
  relative addressing.

doc/doxygen/css/doxygen.css

@@ -0,0 +1,111 @@
+body {
+    font-family: Lucida Grande, Verdana, Geneva, Arial, sans-serif;
+    font-size: 12px;
+}
+
+body {
+    background: #fff;
+    color: #000;
+    margin: 0px;
+    text-decoration: none;
+}
+
+main {
+    padding: 10px;
+}
+
+/* @group Heading Levels */
+
+/*
+h1 {
+    text-align: center;
+    font-size: 150%;
+}
+
+h2 {
+    font-size: 120%;
+}
+
+h3 {
+    font-size: 100%;
+}
+*/
+
+a:link, a:link:hover, a:visited, a:visited:hover {
+    text-decoration: none;
+    color: #0000ff;
+}
+
+a:link img { border: 0; }
+a:visited img { border: 0; }
+a:active img { border: 0; }
+a.menuLefton { color: #0000ff; font-size: 12px; font-weight: bold; }
+td.leftmenu { font-family: verdana, arial, helvetica, sans-serif; text-decoration: none; background: #ddddff; text-align: left; font-size: 14px; height: 20px; width: 200px; }
+
+a.menuTopoff { color: #000000; font-size: 14px; }
+a.menuTopoff:visited { color: #000000; font-size: 14px; }
+a.menuTopoff:hover { color: #0000ff; font-size: 14px; }
+td.topmenu { font-family: verdana, arial, helvetica, sans-serif; background: #ddddff; text-align: center; font-size: 16px; width: 150px; font-weight: bold; }
+
+h1 { font-size: 18px; }
+h2 { font-size: 16px; }
+h3 { font-size: 14px; }
+
+/* formatting for member functions:
+ * Since the OpenFOAM code already has nice line-breaks, wrapping the lines
+ * just looks terrible.
+ * Give a slightly different background to make it easier to find.
+*/
+.memitem {
+    padding: 4px;
+    background-color: #eef3f5;
+    border-width: 1px;
+    border-style: solid;
+    border-color: #dedeee;
+}
+
+.memproto {
+    background-color: #d5e1e8;
+    width: 100%;
+    border-width: 1px;
+    border-style: solid;
+    border-color: #84b0c7;
+    font-weight: bold;
+}
+
+table.memname {
+    width: 100%;
+    background: #f7f7ff;
+    white-space: nowrap;
+}
+
+
+.indexkey {
+    vertical-align: top;
+    background: #f7f7ff;
+}
+
+.indexvalue {
+    vertical-align: top;
+    background: #f7f7ff;
+}
+
+.paramkey {
+    width: 5%;
+}
+
+.memItemLeft {
+    background: #f7f7ff;
+}
+
+.memItemRight {
+    background: #f7f7ff;
+}
+
+.mdescLeft {
+    margin: 0px;
+}
+
+.mdescRight {
+    font-style: italic;
+}