Improve Rule Converter logic so that it can derive undeclared random variable declarations

[GoogleCodeExporter]

You can often figure out undeclared random variable declarations (determining 
the sort for the arguments is the tricky part) from the usage of their 
arguments in other random variable usages that have explicit declarations 
associated with them in a model (the high level rule language). Add support for 
this to the Rule Converter logic so that the user need not explicitly call out 
every declaration.

Original issue reported on code.google.com by [email protected] on 14 Jun 2013 at 9:48