Move the contents of wsar_html/core to wsar_html. Create tag files for

Move the contents of wsar_html/core to wsar_html. Create tag files for
core, epan, and ui, and link them to each other to varying degrees. This
seems to be the best way to organize our documentation. The alternative
is to switch to a single doxygen.cfg and manually add files to different
groups or sections.

Add a wireshark.dox file which contains markup for the main page. Add
.dox and .txt to svnadd. Clean up our tag files. Force wsar_html to
rebuild each time.

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@49091 f5534014-38df-0310-8fa8-9805f1628bb7