HBASE-11331 [blockcache] lazy block decompression

When hbase.block.data.cachecompressed=true, DATA (and ENCODED_DATA) blocks are
cached in the BlockCache in their on-disk format. This is different from the
default behavior, which decompresses and decrypts a block before caching.
HBASE-11932 Docbook html-single build improvements
HBASE-11942 Fix TestHRegionBusyWait
HBASE-11934 Support KeyValueCodec to encode non KeyValue cells. (Anoop Sam John)