update the list of copyright holders

this seem to having not been done in a while. Also, the script which
creates the list has been improved.

COPYING

@@ -7,36 +7,36 @@ also includes version three of the GPL.
 The following people have contributed non-merge commits and may for
 this reason hold part of the copyright:
 
-Andreas Lauser (2008 - 2017)
+Andreas Lauser (2008 - 2018)
 André Brodtkorb (2015 - 2017)
-Arne Morten Kvarving (2013 - 2016)
-Atgeirr Flø Rasmussen (2014 - 2017)
+Arne Morten Kvarving (2013 - 2018)
+Atgeirr Flø Rasmussen (2014 - 2018)
 Benjamin Faigle (2010 - 2014)
-Bernd Flemisch (2008 - 2012)
-Bård Skaflestad (2013 - 2014)
+Bernd Flemisch (2008, 2010 - 2012)
+Bård Skaflestad (2013, 2014)
 Christoph Grueninger (2012)
 Felix Bode (2010)
-Holger Class (2011 - 2012)
+Holger Class (2011, 2012)
 Jean-Paul Balabanian (2016)
 Joakim Hove (2013 - 2017)
-Jochen Fritz (2008 - 2010)
+Jochen Fritz (2008, 2010)
 Jørgen Kvalsvik (2014 - 2017)
 Kai Bao (2017)
 Katherina Baber (2010 - 2012)
-Klaus Mosthaf (2008 - 2012)
+Klaus Mosthaf (2008, 2010 - 2012)
 Kristian Flikka (2014)
 Lena Walter (2010)
-Liu Ming (2014 - 2016)
-Markus Blatt (2013 - 2015)
-Markus Wolff (2008 - 2012)
-Melanie Darcis (2008 - 2010)
+Liu Ming (2014, 2016)
+Markus Blatt (2013 - 2015, 2017)
+Markus Wolff (2008, 2010 - 2012)
+Melanie Darcis (2008, 2010)
 Ove Sævareid (2015)
 Philipp Nuske (2010 - 2012)
 Pål Grønås Drange (2016)
 Robert Klöfkorn (2015 - 2017)
 Rohith Nair (2017)
-Roland Kaufmann (2013 - 2014)
-Tor Harald Sandve (2015 - 2017)
+Roland Kaufmann (2013, 2014)
+Tor Harald Sandve (2015, 2017)
 Vishal Jambhekar (2012)
 
 The following institutions and companies have financially supported