statsd.upstart: exec to remove parent shell from process list

Changes ps output from:

1234 _statsd sh
1235 _statsd \_ statsd /etc/statsd/localConfig.js

to just one second line without intermediate shell process waiting for node.
Merge pull request #429 from temoto/patch-1

statsd.upstart: exec to remove parent shell from process list
Refactorize backend interface
Add fake graphite server for utility
Use new interface in repeater backend
Avoid global variables
Avoid global variables
Fix prefixStast