- moved logic into a Missing singleton
- shouldn't try to download duplicates anymore, only requests a hash
once every 5 minutes and not from the same host
- removed obsoleted variables
- the "Objects to be synced" in the Network tab should now be correct
- removed some checks which aren't necessary anymore in my opinion
- fix missing self in Throttle (thanks landscape.io)
- minor refactoring, made it into singleton instead of a shared global
variable. This makes it a little bit cleaner and moves the class into
a separate file
- removed duplicate inventory locking
- renamed singleton.py to singleinstance.py (this is the code that
ensures only one instance of PyBitmessage runs at the same time)