Add setting to throw exception in non-interactive mode if some params are missing

This PR covers #63 and provides new `exception-if-missing` configuration option. 

By default the behavior of script handler is the same as current. But when `exception-if-missing` option is set to `true` ParameterHandler will throw an exception when some parameters are missing. This is very useful during build/deploy process (executed for example on build/ci servers) when it is needed only to validate `parameters.yml` file before installing the application and abort the process when something went wrong, but not to change it's original content in any way.
 
This behavior affects only non-interactive mode.