Standardize input representation of phonemes

[timmahrt]

Phones in the ISLE dictionary are in IPA. There is no constraint about what the input to ISLE is. pysle tries to smudge the input to be ipa-like but this is kindof hidden to the user. Non-IPA representations probably work sometimes but this is a dangerous assumption.

It's also possible that some parts of the code forgot this fact and assume the input is NOT IPA.

The input representation /is/ preserved in the output, so that is good at least.

Seems like a headache to validate everything is working ok.

[timmahrt]

After closer investigation

• the isle dict itself is IPA
• there is IPA-specific code (eg search functionality)
• most code is representation-neutral, although using non-IPA will lead to silently degraded/unexpected results

Helpful action items:

• Requiring IPA (or requiring a switch so the user has to acknowledge the risk ie ipaInput attributes)
• Conversion tools for switching between representations