#157- Progress on loading snapshot: no technical details and single progress

http://www.intellij.net/tracker/netprofiler/viewSCR?publicId=157
1. Users do not understand techical details like "Creating valid sigatures cache" and the like. Do not expose such details in the progress.
2. Have a single progress window on loading snapshots instead of something like 3 progress windows one after another. This single progress window should show the total progress to give user some estimation when the loading will be finished.