Fix an edge case in HBase 0.96 one-shot scanners.

This bug was introduced in b0113971: with HBase 0.95+ we have the
ability to start retrieving results in the same RPC as the one opening
the scanner.  However, if that RPC returns nothing because the scanner
didn't match any row in the first region, we invoked the callback with
an empty list of results in argument, which is not supposed to happen.

Factor out some code to properly handle scanners reaching the end of
their region, even if that happens during the first RPC.
Add/improve a few toString() methods.
Fix accesses to "hbase:meta".

In HBase 0.96, accesses to "hbase:meta" must be treated like accesses to
"-ROOT-" in HBase 0.94 and earlier.  The code responsible for locating
the region of a given table/key pair was missing a special case test for
HBase 0.96.

The code doing .META. lookups was also referring to the old table name,
and while this didn't matter with HBase 0.96 because the name isn't used
in the RPC's serialization, it caused some confusion while debugging.
Make Scanner usable with -ROOT- / hbase:meta.

There was a pre-existing bug that prevented Scanners from being used on
"-ROOT-" (if HBase 0.94 and earlier) or "hbase:meta" (if HBase 0.96+).

Explicit row locks (removed in HBase 0.95+) were also affected.
Add support for prefetching the meta region.

Resolves OpenTSDB/asynchbase#68.

Signed-off-by: Benoit Sigoure <tsunanet@gmail.com>
Handle an edge case with `prefetchMeta' related to 0.96 compatibility.
Update NEWS/THANKS/AUTHORS.
Upgrade to Netty 3.7.0.