DTDDoc font size demo

actual 0.0.11 = 11px, 13px, 18px

Proposals :

• CSS small = small, medium, x-large
• CSS medium = medium, large, xx-large
• like javadoc (font size only) = (nothing), larger, x-large
• really like javadoc (as much as possible)

Remark : the tree on the left side is changed as well