Log Message:
Updated gnucash to 2.6.15.

GnuCash 2.6.15 Release 2016-12-18

The GnuCash development team proudly announces GnuCash 2.6.15, the
fifteenth maintenance release in the 2.6-stable series.

The following bugs are fixed:

      Bug 340991 - Default price source for reports not good.
      Bug 516920 - Scheduled trasaction calendar popup off screen.
      Bug 685329 - Crashes on non-existent date.
      Bug 769124 - Australian (GMT-10) OFX transactions imported have
                   previous day's date.
      Bug 770364 - Sign of Value in Lots in Account window seems inconsistent.
      Bug 771246 - Set Invoice/Bill items date correctly from imported CSV.
      Bug 771617 - Build fails because test test-report-utilities is
    	           sensitive to time of day/timezone.
      Bug 772313 - Invalid DOCTYPE in report generation.
      Bug 772369 - Replace use of guile's internal date/time functions.
      Bug 772382 - Date off-by-one after DST change.
      Bug 772484 - Segfault on Transaction edit.
      Bug 773808 - Export Report Crash.
      Bug 774237 - FTBFS under some timezones (eg. GMT-14).
      Bug 775368 - "Average cost" price source problem.
      Bug 775385 - Confusing error message which includes the text "file \ 
file".
      Bug 775567 - Importing QIF file from PayPal crashes GnuCash 2.6.14
                   on Windows XP service pack 3/
      Bug 775912 - Tips of the Day shows content only once very 3 times.

Other repairs that weren't marked as bugs in git:
      Fix report html header
      Changed the default value for date format in Business Options
      Change report resizing when not in view
      Add an image for the report tab
      Show empty business splits in lot viewer
      Business check & repair - correct lot invoice state
      When juggling business splits while scrubbing set both value and amount
      Update progress bar while running Check & Repair
      Remove lot from account while deleting the lot
      Ensure that the Namespace combo box is initialized to a valid iter.
      Fix CSV importer to handle GMT + 13 Timezone (New Zealand Daylight
      Fix broken german account template 'Kontenrahmen für
           Wohnungswirtschaft'.Time).

Translation Updates: Danish, German, Serbian