Making nesthdb easier to run

[vuphan314]

@hmarkus

I can now run nesthdb.py on my laptop without errors.

Summary of my changes:

1. I updated config.json in the nesthdb branch with config.json from your Dropbox version.
2. From your Dropbox version, I added projMC-wrapper.py. I made it use python3 (instead of python2) and open files in text mode (instead of binary mode).
3. In config.json, I changed some file paths (htd, sat_solver, and preprocessor) to bin/*, where bin/ is a git-ignored dir.
4. I added helper.py, which converts relative paths in a parsed config into absolute paths so that nesthdb.py can be executed from a different working dir.
5. In nesthdb.py, I added a handle to the logger so that some info will appear in stdout in addition to stderr.