simplified README, added database schema

Simplified and verified README
added schema for sqlite3 db

However, even with the database initialized using the attached schema, python -m utils.run_scan fails very early.

meyers@tinylappy:~/Dropbox/Code/card_scan$ python -m utils.run_scan
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
Traceback (most recent call last):
  File "/usr/lib/python2.7/runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/home/meyers/Dropbox/Code/card_scan/utils/run_scan.py", line 44, in <module>
    next_box = session.query(func.max(sqlalchemy.cast(InvCard.box, sqlalchemy.Integer))).first()[0] + 1
TypeError: unsupported operand type(s) for +: 'NoneType' and 'int'