Add lzma compressor, compression level get/setters

Added vtkLZMADataCompressor, which provides better lossless compression ratios compared to existing vtkDataCompressor subclass objects. Implementing CompressionLevel get/setters at vtkXMLWriter to control tradeoff between compression filesize and compression write performance at a level that is accessible to Python via paraview.simple. CompressionLevel generalized for vtkDataCompressor type objects. CompressionLevel values from 1 to 9 are valid, where 1 optimizes write performance and 9 optimizes filesize. Since different compressors use "compression level" to affect compression properties differently, each vtkDataCompressor type is implemented to provide a homogeneous interface (ie- CompressionLevel values now affect compressor performance in approximately the same way for all vtkDataCompressor subclass objects)