Make acid schema checks case insensitive

When reading from an Orc file, SchemaEvolution evolution tries to determine if this is an Acid compliant format by comparing field names with Acid event names in SchemaEvolution.checkAcidSchema. Would be good to make this comparison case insensitive.
This requirement comes in from HIVE-20699 where a Hive query is being used to run compaction (and hence write the compacted data to the bucket files via a HiveQL query). Since hive converts all column names to lower case, the compacted files end up with lower case Acid schema columns. The change is much simpler when made in Orc.