Update the SIS Javadoc stylesheet for JDK8. In this commit, we also modify the way stylesheet is provided:
instead than overwriting the standard stylesheet with our own, we keep the standard stylesheet and provide
a separated file which overwrite only the part that we need. This protect us from future stylesheet change
in the JDK (there is some changes from JDK 7 to JDK 8) and also avoid the licensing issue of commiting a
file derived from the Oracle file on the SVN. The inconvenient is that the standard javadoc tool is not
designed for working that way: it unconditionally overwrite the standard stylesheet with whatever we provide.
To workaround this issue, we had to provide our own doclet which modify the behavior of the '-stylesheet'
option before to delegate the work to the standard doclet.


git-svn-id: https://svn.apache.org/repos/asf/sis/branches/JDK8@1589201 13f79535-47bb-0310-9956-ffa450edef68