add support for VCF v4.0

git-svn-id: svn+ssh://svn.internal.sanger.ac.uk/repos/svn/pathsoft/artemis/trunk@14402 ee4ac58c-ac51-4696-9907-e4b3aa274f04

ChangeLog

 Version 12.+
+	Add support for VCF v3.3 and v4.0.
+
 	Add option to show combined coverage plots for multiple BAMs.
 
 	Add show_forward_lines and show_reverse_lines as options for switching