doc module: style h[1-6], table and code

Headers have different sizes
Tables have borders
Table headers are left-aligned
Codes are displayed inline (except inside pre) and have scrollbars if necessary

refs #6484
fixes #6632

modules/doc/application/views/scripts/icingaweb/chapter.phtml

@@ -2,6 +2,7 @@
 $urlHelper = $this->getHelper('Url');
 $view = $this;
 ?>
+<div class="chapter">
 <?= preg_replace_callback(
     '/<a\s+(?P<attribs>[^>]*?\s+)?href="#(?P<fragment>[^"]+)"/im',
     function($match) use ($toc, $urlHelper, $view) {
@@ -36,3 +37,4 @@ $view = $this;
     },
     $chapterHtml
 ); ?>
+</div>

modules/doc/application/views/scripts/module/chapter.phtml

@@ -2,6 +2,7 @@
 $urlHelper = $this->getHelper('Url');
 $view = $this;
 ?>
+<div class="chapter">
 <?= preg_replace_callback(
     '/<a\s+(?P<attribs>[^>]*?\s+)?href="#(?P<fragment>[^"]+)"/im',
     function($match) use ($toc, $moduleName, $urlHelper, $view) {
@@ -36,3 +37,4 @@ $view = $this;
     },
     $chapterHtml
 ); ?>
+</div>

modules/doc/public/css/module.less

@@ -1,9 +1,33 @@
-.toc {
-  float: left;
-  width: 33.333%
+// W3C Recommendation <http://www.w3.org/TR/CSS21/sample.html> (except h4)
+h1 { font-size:    2em !important; }
+h2 { font-size:  1.5em !important; }
+h3 { font-size: 1.17em !important; }
+h4 { font-size:    1em !important; }
+h5 { font-size:  .83em !important; }
+h6 { font-size:  .75em !important; }
+
+div.chapter {
+  padding-left: 5px;
 }
 
-.doc {
-  float: left;
-  width: 66.667%
+table th {
+  text-align: left;
+}
+
+table th,
+table td {
+  border: solid 1px lightgray;
+  padding-left: 5px;
+  padding-right: 5px;
+}
+
+code {
+  width: 100%;
+  overflow-x: auto;
+  padding: 0.2em;
+  display: inline;
+}
+
+pre > code {
+  display: inline-block;
 }