Display templating error in cmd.script states

In order to fix this, I made a slight change to the templating system which needs to be discussed and signed off on before this is merged. Before, the templating system was catching templating errors and returning a False result. This result is then logged on the minion by state.py.

The change I made was to raise the exception from the templating system, rather than having it return an error to whatever invoked the templating system.

So, is this the right approach, or could it potentially cause other problems in the state system? If this is a good change, I can make another commit that gets rid of the commented-out line that I left in salt/utils/template.py.