[SPARK-8969][SQL] move type-check from BinaryArithmetic and BinaryComparison to BinaryOperator

[cloud-fan]

also swap protected and override according to scala style guide

[SparkQA]

Test build #37006 has finished for PR 7338 at commit d41e80f.

• This patch fails PySpark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #37003 has finished for PR 7338 at commit 4b92e48.

• This patch passes all tests.
• This patch does not merge cleanly.
• This patch adds no public classes.

[cloud-fan]

retest this please.

[SparkQA]

Test build #37019 has finished for PR 7338 at commit d41e80f.

• This patch fails PySpark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #37043 has finished for PR 7338 at commit f783c19.

• This patch fails PySpark unit tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • implicit class DebugQuery(query: DataFrame) extends Logging
  • class HiveContext(sc: SparkContext) extends SQLContext(sc) with Logging

[rxin]

@cloud-fan next time please separate large cleanups from your change. If it is a line or two of cleanup, it is ok. But it makes this patch harder to review because majority of the diff is just swapping override and protected ...

[cloud-fan]

closing in favor of #7348