[BRLTTY] Fedora dracut module

[Jaroslav Skarvada]

Hi,

proof of concept implementation:
https://src.fedoraproject.org/rpms/brltty/c/5f009fa9a69939c3dc8b6d50c053bb72f02f406d?branch=master

There is a room for improvement, but it seems to work (at least).

It:
- adds to the initramfs what the user has enabled on the host system
 (drivers, tables, ...), it can be overridden by setting environment variables
- starts brltty in dracut shell
- stops brltty during cleanup phase
- allows user to override active driver and it's parameters during boot by
  setting kernel command line parameters

comments are welcome

thanks & regards

Jaroslav