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
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.
htmlreport: 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.
Merge pull request #186 from matthiaskrgr/css2

html-report CSS