Implement a new metric option 'reset_after_push' which will make uWSGI...

reset to 0 the given metric after it's been pushed to the stats backend.
This is handy when you want to automatically reset counters every 'freq'
seconds.
Update all plugins so that they bear this functionality (reset_after_push)
Use the wlock when the value is reseted
Merge pull request #630 from btall/reset-after-push

Implement a new metric option 'reset_after_push' which will make uWSGI.....