Add TIME_MICROS support to GenericParquetReaders

[ashleycoxley]

Closes #482

[rdblue]

We avoid wildcard imports because it isn't clear where symbols are coming from and there is potential for collision. Could you roll back this change? (As well as the additional newline, we don't use breaks in imports either.)

[ashleycoxley]

Yes!

[rdblue]

Thanks for working on this, @ashleycoxley!

[rdblue]

Looks like there are checkstyle violations:

[ant:checkstyle] [ERROR] /home/travis/build/apache/incubator-iceberg/data/src/main/java/org/apache/iceberg/data/parquet/GenericParquetReaders.java:26: Extra separation in import group before 'java.time.Instant' [ImportOrder]
[ant:checkstyle] [ERROR] /home/travis/build/apache/incubator-iceberg/data/src/main/java/org/apache/iceberg/data/parquet/GenericParquetReaders.java:379:44: '{' at column 44 should have line break after. [LeftCurly]
[ant:checkstyle] [ERROR] /home/travis/build/apache/incubator-iceberg/data/src/main/java/org/apache/iceberg/data/parquet/GenericParquetReaders.java:379:103: '}' at column 103 should be alone on a line. [RightCurly]

[rdblue]

Merged! Thanks for the quick updates, @ashleycoxley!

If you'd like to open a PR for TIME_MILLIS as well, I can help review it.

[aokolnychyi]

I've created an issue to support TIME_MILLIS so that we don't forget.

[rdblue]

Thanks, Anton!

[ashleycoxley]

Thanks both! I'll plan to pick that up soon.