Add three Danish braille tables

[dkager]

Link to issue number:

Fixes #2835.

Summary of the issue:

There are a few Danish braille tables in liblouis that are not yet in NVDA.

Description of how this pull request fixes the issue:

This adds three new Danish braille tables, both input and output:

1. 8-dot computer braille
2. 6-dot grade 1.5 (grade 2l)
3. 8-dot grade 1.5 (grade 2l)

Motivation for including these tables is in #2835 (comment). In short:

• The computer braille table is obviously useful for screen readers.
• The two grade 1.5 tables are used by e.g. deaf-blind people. Their availability would be unique to NVDA.

Testing performed:

The tables themselves are unit tested in liblouis. I tested that they appear in the braille settings dialog and that they can be activated from there.

Known issues with pull request:

According to @BueVest:

• The tables are ready but not set in stone, i.e. if the Danish braille committee makes changes.
• The name "grade 1.5" is a bit unfortunate. For the Danish translation of NVDA a more appropriate name would be used.

Change log entry:

New Features:

• Three new Danish braille tables have been added: 8-dot computer braille, 6-dot grade 1.5 and 8-dot grade 1.5. They are available for braille input and output.

[dkager]

Closing for now because:

1. The computer braille table is part of NVDA 2017.3.
2. There isn't much evidence that the grade 1.5 tables are actually wanted.