Cherokee: Adjust base pitch to be higher (seems to effect consonents).

Also removed the pause after each syllable as it no longer seems needed
with the higher base pitch.

Adjusted the tone start/stop values based on Praat pitch analysis
on the newer base pitch.

Add initial support for Pyash languagege, more info:

* https://www.academia.edu/34133204/Pyash_One_Language_to_Unite_Them_All
* https://gitlab.com/liberit/pyac

This reverts commit 6042eb8d1e.

The change causes an issue with `pt-BR` and possibly other languages
and voices.

A new 'hyw' language code has been registered for Western Armenian,
and the arevela and arevmda variant subtags have been deprecated.

This still accepts the hy-arevela and hy-arevmda language tags, but
uses the preferred names for the language files.

This reverts commit 0f55204522.

This breaks using voice files like mb-de5-en. It could also use
named values for the stress rules (e.g. 'first-syllable').

Keyword stressRule in voices.c handles setting langopts->stress_rule.

tr_languages.c still contains the setting for some languages that don't have a language file yet.

Contributes to:
Issue #218, https://github.com/espeak-ng/espeak-ng/issues/218

Contributes to:
Issue #218, https://github.com/espeak-ng/espeak-ng/issues/218

Changes:
language files have a new keyword letterVowel. It can be a latin alphabet from a-z or a hex value (used by bulgarian).
Errors in parsing the values are only reported, nothing is done about them.

About testing:
I haven't noticed any differences in the output audio with letterVowel set or unset in any tested language. The code seems to work and the correct bits seem to be set, but I don't know how to confirm from the final audio.

TODO:
1. Write better documentation in docs/voices.md
2. The code uses new_translator. Should it use translator instead?