enhancement: averages for bar chart reports

[Herbert Thoma]

Matthias Gruhn suggested on the German GnuCash list:

Add averages to the income and expense bar chart reports just like it was
introduced for the income and expense pie chart reports in r19253

I created bug #639259 and added a patch that implements this.
The patch introduces one new string. Please add this to the
translations.

  Herbert.
-- 
Herbert Thoma
Dipl.-Ing., MBA
Head of Video Group
Multimedia Realtime Systems Department
Fraunhofer IIS
Am Wolfsmantel 33, 91058 Erlangen, Germany
Phone: +49-9131-776-6130
Fax:   +49-9131-776-6099
email: tma at iis.fhg.de
www: http://www.iis.fhg.de/