[unicodedata] add new module and 'script' function
[unicodedata] add new module and 'script' function

The new `fontTools.unicodedata` module re-exports all the public
functions from the built-in `unicodedata` module, and also adds
additional functions.

The `script` function takes a unicode character and returns the
script name as defined in the UCD "Script.txt" data file.

It's implemented as a simple binary search, plus a memoizing
decorator that caches the results to avoid search the same
character more than once.

The unicodedata2 backport is imported if present, otherwise
the unicodedata built-in is used.

googlefonts/fonttools,fonttools/fonttools