Remove files from old budgeting code that are no longer used.

[David Hampton]

Log Message:
-----------
Remove files from old budgeting code that are no longer used.

Tags:
----
gnucash-gnome2-dev

Removed Files:
-------------
    gnucash/src/engine:
        gnc-budget-book-p.h
        gnc-budget-book.c
        gnc-budget-book.h
        gnc-budget-cat-p.h
        gnc-budget-cat.c
        gnc-budget-cat.h
        gnc-budget-p.h
        gnc-budget-period-p.h
        gnc-budget-period-value-p.h
        gnc-budget-period-value.c
        gnc-budget-period-value.h
        gnc-budget-period.c
        gnc-budget-period.h
    gnucash/src/gnome:
        dialog-budget-category.c
        dialog-budget-category.h
        dialog-budget-list.c
        dialog-budget-list.h
        dialog-budget-workbench.c
        dialog-budget-workbench.h
        druid-budget-create.c
        druid-budget-create.h
        gnc-budget-gui.h
    gnucash/src/gnome-utils:
        gnc-budget-list-tree-model.c
        gnc-budget-list-tree-model.h
        gnc-budget-tree-model.c
        gnc-budget-tree-model.h