Added passing arrays by reference
-Tetra interpreter now properly passes arrays to for loops and functions by reference
-Tetra interpreter now handles multidimensional arrays
-Tetra interpreter now supports unary operations

Other minor fixes and additions
-Added an explicit change to frontend/node.cpp as per request
-Plugged a memory leak in tData copy assignment
-added in further programs to the interpreter/testProgs directory to demonstrate new functionality
-renamed tData.cpp to tData.h

Interpreter does not yet support returning arrays by reference (still returns by value)