start a new branch for data-path detection
extracting data paths
able to output a graph, but lots of control ports, clk and rst are not removed
add the deafult nodes back to hierarchical RRG
clk is removed from the data path graph
fix the wrong rst edge type
extract datapath according to output only
seems datapath extraction is ready, need further optimization
Merge branch 'datapath' into dev
Merge branch 'dev'