htmlreport: give warnig boxes ("HTML_ERROR") smaller frame and padding so they don't overlap each other if there is another one in next line.

borderwith: 2px -> 1px
padding:    3px -> 1px
font-size: 13px -> 11px
htmlreport: use "overflow: auto" in body. This prevents the <pre> text from overlapping the "page" class. Instead a scrollbar is displayed at the bottom of the element.
Also slightly reduce font size from 13 to 12.
htmlreport: remove page-header and page-footer, change grey-tone of the code-line numbers, set page-width to auto and adjust margin.
htmlreport: fix page border, seperation border at right side of linenumbers.
htmlreport: allow content to be wider and reduce height of menu box. If we need STILL more width for the content box, the scroll bar is added as fallback anyway.