Is your feature request related to a problem or challenge? Please describe what you are trying to do.
After #256 we completely ignore NaNs in parquet statistics. However, there are good reasons to fully order floats and include NaN somewhere:

• Databases usually need it, see sql: NaN = NaN (in Postgres) cockroachdb/cockroach#18860 and if DataFusion wants to follow the Postgres dialect we will have the same issue there
• Other parquet users are interested as well: PARQUET-1222
• Just ignoring NaN is kinda having an implicit NULL for float while we already have a NULL-mask

Describe the solution you'd like
Put NaNs at the end of the float scale, so the order is:

1. -inf
2. "ordinary" numbers
3. +inf
4. NaN

Describe alternatives you've considered
Keeping the status quo (aka current master).

Additional context
.