Bug 7585 - Correct MARC 008 Value Builder Char 06 Default

Bug 7585 - Correct MARC 008 Value Builder Char 06 Default

This patch changes the default value of the 06 char in 008
from 't' to 'b.' This change allows for a valid 008 field
if no dates are entered in 07-14.

To test:

1. Create a new MARC record (prior to patch application).
2. Click on the 008 field to auto-populate.
3. Note that the 06 char is 't'.
4. Apply patch.
5. Create a new MARC record.
6. Click on the 008 field to auto-populate.
7. Note that the 06 char is now 'b'.

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Confirm fix works per test plan.