Store some more debugger settings

- Make settings of debugged executables persistent (Tripel of assembly, workingdirectory and arguments), initialize with last debugged executable.
- Make breakpoints persistent. More exactly, store all bookmarks which have an exported implementation of IBookmarkPersistence. This is done per assembly list. The load/save is triggered by debugger plugin because BookmarkManager as part of ILSpy.SharpDevelop.LGPL has no access to ILSpySettings or MainWindow.
- Sort the entries in breakpoint panel