[SPARK-5465] [SQL] Fixes filter push-down for Parquet data source

[liancheng]

Not all Catalyst filter expressions can be converted to Parquet filter predicates. We should try to convert each individual predicate and then collect those convertible ones.

[SparkQA]

Test build #26254 has started for PR 4255 at commit 14ccd37.

• This patch merges cleanly.

[SparkQA]

Test build #26254 has finished for PR 4255 at commit 14ccd37.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[AmplabJenkins]

Test PASSed.
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Test PASSed.