nwztools/database: misc improvements

* make gen_db.py work on Windows/Python 2

- use hashlib module instead of md5sum, also don't rely on / for file path
- don't use 'file' for a variable name

* fix parse_nvp_header.sh for older kernels

pre-emmc kernel sources use a slightly different #define format; adjust
regexp to catch it.

* add nwz-x1000 series NVP layout (from icx1087_nvp.h)

some new tags have no description, alas the driver doesn't have
them :/

*  minor fixes to nvp/README

fixed typos/wording

Change-Id: I77d8c2704be2f2316e32aadcfd362df7102360d4
8 files changed