Move all data files into a subdirectory.
Pull all of the embedded data out of scansys.py.

* sorthdr.py and setcommon.py merged into scansys.py
* prerequisites now defined in an .ini file
* compute the headers-to-probe list from data/b-*, only
* remove data/r-*
* add some entries to data/b-ucom so that the probe set is unchanged
* scansys.py now does proper command line parsing; can be told to look
  for data/ and prereqs.ini elsewhere
Make Python scripts executable.
Merge prep side A: match filename changes from side B
Merge prep side B: match move to subdir from side A
Merge tblgen work from last week
License tagging; move web resources to subdirectory.