jme3-alloc-examples: added basic tech-demos

[pavly-gerges]

This PR adds the following tech-demos:

• TestNativeBufferUtils: tests the basic api functionalities (allocation/deallocation) on a single main thread.
• TestDirtyMultithreading: tests the api functionalities on 20 java.nio.ByteBuffer across 3 threads, an allocation thread, an initialization thread and a de-allocation/destroy thread.
• TestJvmCrashlogs: tests the jvm monitor crash; when trying to write to a previously destroyed buffer.
• TestMemoryCopy: tests copying memory from a buffer to another (deep copy).
• TestMemorySet: tests initializing the buffer memory with zero and erasing the buffer for subsequent read/write operations if needed or in case the buffer carries sensitive data (as user-credentials).