Improve htdocs-moved message and readd trunk and beta branch directories.

A similar message has been added in those directories to point users that run svn update to the proper new locations instead of generating an error

git-svn-id: svn+ssh://svn.gnucash.org/repo/htdocs/trunk@23008 57a11ea4-9604-0410-9ed3-97b8803252fd