Improve exceptions/error reports

[seancorfield]

Although ex-data helps a bit in debugging a deeply nested parse failure, it doesn't provide any context. Walking the stack for invokeStatic on honey.sql$format_* calls might be a quick win in getting a "path" into the expression (although it still wouldn't really give expression context).

Instrumenting major formatters to push their expression arguments on a dyn Var bound stack would really help here but would touch a lot of code.

Needs some deep thought!

[seancorfield]

I'm beginning to lean toward the stacktrace walker/formatter after thinking about this for 24 hours...

[seancorfield]

After some REPL experimentation, that doesn't help at all in relatively simple cases.