Fixes to send_nsca() in Plugins.simple

Added the ability to specify location of send_nsca binary and cfg. Renamed ncsahost to nscahost. Added documentation about possible arguments. Switched from using popen to runCommand() provided in Utils.
Merge pull request #116 from awiddersheim/fix_nsca_bin

Fixes to send_nsca() in Plugins.simple

There are minor issues regarding send_nsca now running arbitrary strings, i will create an issue for that.

otherwise the patch is good.

Ultimately i think send_nsca would live in Utils somewhere but that is a story for another day.