Add support for String parameters

[alorence]

For the moment, instances with String arguments are not managed correctly when the design is run in Jade.

For example, in orc-apps/HelloWorld/Example, instances CopyTokenA and CopyTokenB have an argument name set to respectively "first" and "second".
In the corresponding actor CopyTokens, there is a parmater String name used in the println.

When this design is run in Jade, here is the output:

Producer (0)
Producer (1)
Producer (2)
LLVM ERROR: Could not resolve external global address: CopyTokenA_name

The parameters of type String are simply ignored by Jade.