Scheduler rename

• Adds strings to scheduling language (though with a very limited character set, there are no special symbols except _, -, and spaces; basically this is intended as strings that are reasonable for function names and file names).
• Adds a rename pass which allows us to rename functions to avoid having to access pass results using generated function names.

juno_samples/fork_join_tests/src/cpu.sch

@@ -15,6 +15,7 @@ cpu(auto.test7);
 cpu(auto.test8);
 
 let test1_cpu = auto.test1;
+rename["test1_cpu"](test1_cpu);
 
 ip-sroa(*);
 sroa(*);