+workbench, reporegistry: show progress dialog for lengthy startup operations
+Loading the workbench may take a long time, particularly if you have
+repositories located on remote drives. Up until now, the user did not get any
+feedback or visual cue while the workbench is being loaded . The user cannot
+even tell that the workbench is being loaded in the first place!
+With these changes a progress dialog will be shown when the subrepos are being
+loaded by the reporegistry and while the workbench is reopening the repos that
+where open on the last workbench session.
+This informs the user that the workbench is being loaded.
+In addition, once the workbench is loaded, reloading the repo-registry will show
+a progress bar on the status bar.