Improve Evy error handling

[juliaogris]

This is an umbrella issue for all things error handling that need addressing.

Generically: we probably want to fuzz-test for unexpected runtime errors.

Heuristics: we want to come up with a way of suggesting fix for errors.

Tracking: we probably want to track the most common errors.

[juliaogris]

print [1]["a"]

error:

line 1: array index expects num, found string
line 1: expected end of line, found "]"

Should remove second error message.