contrib/tesseract-langs.sh: add script to generate recipes for tesseract languages

This script writes language recipes for tesseract.  It downloads the
listing of available languages and language tarballs from the official
site and writes language recipes tesseract-lang-<lang>_<version>.bb
for each language.

Signed-off-by: Mario Domenech Goulart <mario@ossystems.com.br>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>