Renamed charts.d to plugins.d
Moved stuff around to accomplish it.

charts.d will remain for simple scripts
plugins.d will get a new thread each
Now there are 2 kinds of plugins:

 - plugins.d plugins that are expected to always be in memory and execute
   continiously

 - charts.d scripts that are sourced by the charts.d plugin
   and are all executed together, lowering significantly the resources
   they require (compared to plugins)