Initial changes to budget view.
1) Splits gnc-budget-view.c/.h out from gnc-plugin-page-budget.c.  gnc-plugin-page-budget.c now creates a GncBudgetView and provides the overall UI and integration for it.
2) GncBudgetView changes:
    a) If an account has children but does not have a specific budget value for a period, the sum of the children's budget values will be displayed in gray
    b) Totals column on the right provides total for a budget row (account)
    c) At the bottom, totals lines with total income, total expenses, total transfers (assets+liabilities) and grand total (income - expenses - transfers)



git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@22796 57a11ea4-9604-0410-9ed3-97b8803252fd