[Java] add an util method for buffer's pretty hex dump

[QIvan]

hi! My colleagues had some experiments with Netty and they showed me beautiful logging of byte buffers and I thought that it would be nice to have in aeron for debug purposes.
So I adopted that code for MutableDirectBuffer
results seems like this
for buffer

final UnsafeBuffer buffer = new UnsafeBuffer(new byte[128]);

final int length = buffer.putIntAscii(INDEX, -123);

System.out.println(PrintBufferUtil.prettyHexDump(buffer));

output will be

         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 00 2d 31 32 33 00 00 00 00 00 00 00 00 00 00 00 |.-123...........|
|00000010| 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|00000020| 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|00000030| 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|00000040| 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|00000050| 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|00000060| 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
|00000070| 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
+--------+-------------------------------------------------+----------------+

or for

final byte[] testBytes = "Hello World".getBytes();
final ByteBuffer srcBuffer = ByteBuffer.allocateDirect(testBytes.length);
srcBuffer.put(testBytes).flip();

final UnsafeBuffer srcUnsafeBuffer = new UnsafeBuffer(srcBuffer);

srcUnsafeBuffer.getBytes(0, buffer, INDEX, testBytes.length);

output is

         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 48 65 6c 6c 6f 20 57 6f 72 6c 64                |Hello World     |
+--------+-------------------------------------------------+----------------+

[QIvan]

oh, right, I also made your build.gradle file a little bit more IDE-friendly.

[QIvan]

about licence, my understanding as well as I noticed that original code is from netty project, i kept the header and your code is under the same Apache 2.0 licence there is no problems here.

[normanmaurer]

Sounds good to me 👌

[normanmaurer]

I think you also need to add it it to the notice file (or something similar)

[normanmaurer]

I think you also want to add the agrona license header as well

[QIvan]

Sorry i was out of my desc, thank you @mjpt777 for the tidy up and improvements.
thanks everyone for review and merge!