Add sanity checks and ask user when there are no purpose lines.

[Christian Stimming]

Log Message:
-----------
Add sanity checks and ask user when there are no purpose lines.

2005-05-23  Christian Stimming  <stimming at tuhh.de>

	* src/import-export/hbci/dialog-hbcitrans.c: Add sanity checks and
	ask user when there are no purpose lines.

Modified Files:
--------------
    gnucash:
        ChangeLog
    gnucash/src/import-export/hbci:
        dialog-hbcitrans.c
        gnc-hbci-utils.c
        gnc-hbci-utils.h