Rewrite MWI and CallFlow subscribe handlers based on EventConsumer class.
Also on my test VirtualBox/Debian system Lua function `os.clock` produce
very strange result(delta ~0.015 for 1 second) so I switch to `os.time`.
Now to to stop this background Lua scripts it possible send CUSTOM event
with subclass `fusion::XXX::shutdown`. Where XXX is `mwi` or `flow`.
Usage of EventConsumer class
```Lua
-- create new object with timeout one minute
local events = EventConsumer.new(60000)
-- bind to some FS event
events:bind("SHUTDOW", function(self, name, event) ... end)
-- bind to another FS event with subclass
events:bind("CUSTOM::fusion::mwi::shutdown", function(self, name, event) ... end)
-- handle timeout event
events:on("TIMEOUT", function(self, name) ... end)
--run event loop
events:run()
```
a52e9c3626