Change the way on how we track store file list

Introduces the StoreFileTracker interface to HBase. This is a server-side interface which abstracts how a Store (column family) knows what files should be included in that Store. Previously, HBase relied on a listing the directory a Store used for storage to determine the files which should make up that Store. After this feature, there are two implementations of StoreFileTrackers. The first (and default) implementation is listing the Store directory. The second is a new implementation which records files which belong to a Store within each Store. Whenever the list of files that make up a Store change, this metadata file will be updated. This feature is notable in that it better enables HBase to function on storage systems which do not provide the typical posix filesystem semantics, most importantly, those which do not implement a file rename operation which is atomic. Storage systems which do not implement atomic renames often implement a rename as a copy and delete operation which amplifies the I/O costs by 2x. At scale, this feature should have a 2x reduction in I/O costs when using storage systems that do not provide atomic renames, most importantly in HBase compactions and memstore flushes. See the corresponding section, "Store File Tracking", in the HBase book for more information on how to use this feature.