Add batched meta writes method to AstyanaxWriter
Add batched meta reads method to AstyanaxReader
Add batched interfaces for meta fetch and push in MetadatIO
Add ability to use the batched methods for meta fetch and push for metadata cache
Add instrumentation around scanMetrics and checkMeta
Log the entire exception in RollupType cacher on cache exceptions
Place holder methods in MetadataCacheIntegrationTest
Add AstyanaxMetadataIO integration test
Add test cases for batched mode for meta reads and writes
Merge pull request #308 from lakshmi-kannan/bf_batched_meta_reads_writes_merge

RFR: Batched meta reads and writes