Wrapper around a lazily instantiated, local HTable.
Previously, we had used various row and batch caches. However, this ends up being very complicated when attempting manage updating and invalidating the cache with no real gain as any row accessed multiple times will likely be in HBase's block cache, invalidating any extra caching we are doing here. In the end, its simpler and about as efficient to just get the current state of the row from HBase and let HBase manage caching the row from disk on its own.