Brltty support for dracut

This module provides brltty functionality in the initrd.

Module pickups user settings from system and install

necessary files like drivers and used text tables to initramfs.

For now the module is reliably functional from phase pre-mount

in earlier phases the module is not functional

TBD fix functionality from earlier phases than pre-mount

Module in instalation takes some options from environment variables.

BRLTTY_DRACUT_INCLUDE_DRIVERS forces include of screen or braille

driver

example:

BRLTTY_DRACUT_INCLUDE_DRIVERS=bpm beu

BRLTTY_DRACUT_INCLUDE_TEXT_FILES forces include of text tables

example:

BRLTTY_DRACUT_INCLUDE_TEXT_FILES=kok.ttb lv.tti

BRLTTY_LOCALE needs to be used when building initram image

to install used text table 

see https://bugzilla.redhat.com/show_bug.cgi?id=1584036

example

BRLTTY_LOCALE=cs_CZ.UTF-8

Module allows to override some settings from grub

mainly for debugging purposes

brltty.braille_parameters

example:

brltty.braille_parameters="auth=none,host=IP:0"

brltty.braille_driver

example:

brltty.braile_driver="ba"