Changes

Some changes. These things change how FragMe works or affects the documentation:

• Changed the name CheckThread to JoinThread. One JoinThread is created for each peer that joins the group, and it terminates when the setup is complete.
• Changed the names of several flags in PeerManagerImpl and ControlCenter to more accurately reflect what they represent.
• During start up, JoinThread waits on spaceForMeHasBeenAllocated (Hashtable) and peerAddressToNameTable (Hashtable, as before). ControlCenter waits on allPeersHaveFinishedSetup, which is updated every time a JoinThread is started or ended.