to use the bisect built-in module we need to have two separate
tables, one with the ranges themselves (which we pass to bisect
to get an index) and the other containing the script name for
each range.
Also, allow the buildUCD.py script to load data files from a
local directory, e.g. to allow downstream maintainers to rebuild
the generated modules from local files instead of downloading
from Unicode website.
The script currently only parses the Scripts.txt file and
generates a new python module `fontTools.unicodedata.scripts`
containing a `SCRIPT_RANGES` list of tuples, each containing
the range and the corresponding script name.
