Add support for building Dash or Zeal compatible docset bundles.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxPython/Phoenix/trunk@75773 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Restructure the page headers and how they are tweaked so we don't
have the weird wrapping problems, unless the user has a weirdly
sized browser.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxPython/Phoenix/trunk@75774 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775