Use misc.Unsafe for speed improvements

[JasperGeurtz]

Avoids java bounds checking, testing in experimental branch.

Results are promising

Even for simple retrieval of ints/bytes (NOT objects, e.g. were BWMirror is much slower)

Performance results

BWMirror - JNI
1000000 calls in : 23.5 ms
1000000 calls in : 23.28 ms
1000000 calls in : 21.68 ms
1000000 calls in : 20.78 ms
1000000 calls in : 20.5 ms
1000000 calls in : 21.33 ms
1000000 calls in : 20.35 ms
1000000 calls in : 22.86 ms
1000000 calls in : 21.34 ms
1000000 calls in : 21.3 ms
1000000 calls in : 22.61 ms

JBWAPI - Buffer

1000000 calls in : 18.11 ms
1000000 calls in : 16.92 ms
1000000 calls in : 15.82 ms
1000000 calls in : 17.54 ms
1000000 calls in : 19.19 ms
1000000 calls in : 23.89 ms
1000000 calls in : 16.63 ms
1000000 calls in : 23.32 ms
1000000 calls in : 15.7 ms
1000000 calls in : 15.77 ms
1000000 calls in : 16.62 ms

JBWAPI - Unsafe

1000000 calls in : 8.15 ms
1000000 calls in : 6.37 ms
1000000 calls in : 3.93 ms
1000000 calls in : 4.11 ms
1000000 calls in : 3.93 ms
1000000 calls in : 4.08 ms
1000000 calls in : 4.05 ms
1000000 calls in : 4.0 ms
1000000 calls in : 4.01 ms
1000000 calls in : 3.93 ms
1000000 calls in : 4.12 ms

C++ (Client) (thanks to @N00byEdge)
1000000 calls in 2.78177ms
1000000 calls in 3.05884ms
1000000 calls in 3.51817ms
1000000 calls in 2.8359ms
1000000 calls in 3.92982ms
1000000 calls in 5.74114ms
1000000 calls in 3.34673ms
1000000 calls in 3.29377ms
1000000 calls in 4.41666ms
1000000 calls in 3.73234ms