Bug 728136 - Rate in Job

Added rate in job for automatic filling in price in customer invoices and vendor bills.

	modified:   src/business/business-gnome/dialog-job.c
	modified:   src/business/business-gnome/gtkbuilder/dialog-job.glade
	modified:   src/business/business-ledger/gncEntryLedgerLoad.c
	modified:   src/engine/gncJob.c
	modified:   src/engine/gncJob.h
	modified:   src/engine/test/test-job.c