Allow the user to select the initial date cursor position in the settings dialog

As default the cursor position is set to the day part of the date field.

This patch contains a fix to be compilable with gcc 4.8.

CCBUG:374123
BUG:389631
FIXED-IN:4.8.2

Test Plan: compiled and tested on linux

Reviewers: #kmymoney, tbaumgart

Reviewed By: #kmymoney, tbaumgart

Subscribers: tbaumgart

Differential Revision: https://phabricator.kde.org/D10310