Fix up MATLAB ScriptEngine

* Removed unnecessary while loop
* Instead of using ans, now store script in temporary variable.
Add MATLAB decode implementation

All return values from MATLABControl come back wrapped in Object arrays
to allow for multiple return value functions. In the case that we have
one return value, the decode method will now unwrap this array.
Fix MATLAB context creation in tests

Consolidated context management to setup/teardown methods.