Fix inaccurate heading id generation documentation.

All headings have ids generated, not just `h1`, `h2` and `h3`.

git-svn-id: https://svn.boost.org/svn/boost/trunk/tools/quickbook@85402 b8fc166d-592f-0410-95f2-cb63ce0dd405
Update the import and include documentation.

This is a bit incoherent at the moment. It needs to be rearranged so
that there's a tutorial that introduces the concepts in a more logical
order. But I want to press on with some of the other updates.

git-svn-id: https://svn.boost.org/svn/boost/trunk/tools/quickbook@85403 b8fc166d-592f-0410-95f2-cb63ce0dd405
Update version meta-data documentation.

git-svn-id: https://svn.boost.org/svn/boost/trunk/tools/quickbook@85404 b8fc166d-592f-0410-95f2-cb63ce0dd405
Add explicit ids to heading documentation.

git-svn-id: https://svn.boost.org/svn/boost/trunk/tools/quickbook@85405 b8fc166d-592f-0410-95f2-cb63ce0dd405
Add note about xmlbase.

git-svn-id: https://svn.boost.org/svn/boost/trunk/tools/quickbook@85406 b8fc166d-592f-0410-95f2-cb63ce0dd405
Add new elements in 1.6 to the main documentation.

git-svn-id: https://svn.boost.org/svn/boost/trunk/tools/quickbook@85407 b8fc166d-592f-0410-95f2-cb63ce0dd405