Allow MySQL check configuration via a mysql config file

For more complex configuration (e.g. specifying SSL certificates) it's
useful to use a mysql.cnf instead of specifying flags by hand.
add riak 1.3.2 metrics to monitor new "Overload Protection / Work Shedding" feature
Add CPU percent and threads number metrics
More precise cpu persentage
x2 more precise cpu persentage
Configurable CPU check interval
Add cpu_check_interval for CPU percent usage
Make a pause when restarting the agent to give enough time for the agent to clean itself
Merge branch 'master' of github.com:DataDog/dd-agent
Reduce sleeping time when restart
Update datadog-agent.init
Sleep to give enough time for the daemon to stop cleanly
Allow optional custom tags in SQL Server check.
Made postgres database name configurable.
Fixes issue #523.
bump version to 3.9.3
Merge pull request #646 from morskoyzmey/patch-1

Add CPU percent and threads number metrics
Display a warning if the cpu_check_interval is not a number
Merge pull request #643 from stefan-mees/master

add riak 1.3.2 metrics to monitor new "Overload Protection / Work Sheddi...
Fetch the Mongo database name from the URI.
Merge pull request #657 from DataDog/mongo_db_config

Fetch the Mongo database name from the URI.