Folding txt files into Doxygen output

[Neil Williams]

Log Message:
-----------
Folding txt files into Doxygen output

Tags:
----
gnucash-gnome2-dev

Modified Files:
--------------
    gnucash:
        ChangeLog
    gnucash/src/doc:
        backend-api.txt
        backend-errors.txt
        backup.txt
        books.txt
        budget.txt
        business.txt
        constraints.txt
        currencies.txt
        doxygen.cfg.in
        doxygen_main_page.c
        engine.txt
        g2-architecture.txt
        generic-druid-framework.txt
        guid.txt
        loans.txt
        lots.txt
        multicurrency-discussion.txt
        netlogin.txt
        plugin.txt
        prices.txt
        qif.txt
        tax.txt
        user-prefs-howto.txt
    gnucash/src/engine:
        design.txt
        extensions.txt
        kvp_doc.txt
    gnucash/src/scm:
        startup-design.txt

Removed Files:
-------------
    gnucash/src/doc:
        gnc-commodity.txt