Merge branch 'feature/exec_hlslib_streamingfclayer' of https://github.com/Xilinx/finn into feature/exec_hlslib_streamingfclayer

wrapper attributes must now be declared in the get_nodeattr_types
and accessed using the getter/setters here, all data stored in
ONNX node attributes.

there's lots more testing needed for StreamingFC, so this will
come in handy when writing those new tests

[Code gen] Modified existing hlslib nodes to create temporary directories for their files -> tmp directory name is now class variable