Format models headers according to the KDE guidelines
Purpose of this patch is to tidy up source code headers. Right now we've
got three different types of headers (accountsviewproxymodel.cpp,
payeeidentifier.cpp, kcurrecycalculator.cpp). This patch will
standardize them to one according to
https://community.kde.org/Policies/Licensing_Policy#GPL_Header
Moreover, there are some names in the headers, which have not event
touched the file, so it's false authorship. Those names has been
removed. List of the names to remove has been taken from:
- CVS logs (http://kmymoney2.cvs.sourceforge.net/),
- git logs,
- KMM Sourceforge developer mailing list
(https://sourceforge.net/p/kmymoney2/mailman/kmymoney2-developer/)
- CVS stats
(http://kmymoney2.sourceforge.net/kmymoney2-stats/authors.html)
- ChangeLog of CVS
Differential Revision: https://phabricator.kde.org/D13159