More modifications to incorporate testDecompress into cudpp_testrig
Started establishing function calls for decompress, even though no decompress CUDA code exists yet
Created new header file for declaration of Huffman object structs
Removed decompress_gold.h as functionality from this file was moved entirely to other files
Additional modifications to prepare CUDPP for decompress. CUDPP compiles correctly.

- New HuffmanTreeArray struct that is identical to HuffmanTree struct, except that the nodes are stored in an array. This is so that the HuffmanTreeArray object can be used in CUDPP (CUDA) code.
- Moved HuffmanNode and HuffmanTreeArray declarations to cudpp.h for visibility in CUDPP source files (src/cudpp/...).
- Added code in decompress_gold.cpp to create a HuffmanTreeArray object from a HuffmanTree object.
   - I wanted to do this with a function in the HuffmanTreeArray struct, but HuffmanTree is declared in decompress_gold.cpp and cudpp.h (where HuffmanTreeArray is decared) can only contain C code (no C++).
   - Since HuffmanTree uses std::vector, it contains C++ code and can't be included in cudpp.h (or any CUDPP/CUDA code)
Added a copy function to HuffmanNode (instead of HuffmanNodeArray) to copy the data from a HuffmanNode to HuffmanNodeArray. This way, HuffmanNodeArray stays 100% C code.
Small changes to cudpp_testrig. Unable to make changes in cudpp_testrig.cpp reflect in the compiled output (ie - print statements, code execution)