Design space explorer

[lee30sonia]

• algorithms/explorer.hpp: On-the-fly design space exploration.
• networks/gia.hpp & utils/abc.hpp: Direct interfacing with ABC as a static library (conversion of networks via APIs). Requires CMake option ENABLE_ABC to be turned on, which requires having a compiled libabc.a file (see this repo).
• Various fixes in aig_resub, cut_rewriting and refactoring.
• Adds simulation-guided MIG resub in sim_resub so that it's easier to be called.