Only restore a single mainwindow, based on KMKernel::doSessionManagement in KMail.
Only restore a single mainwindow, based on KMKernel::doSessionManagement in KMail.

svn path=/trunk/kdepim/; revision=245119

lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi,lefou/kdepim-noakonadi