Created Benchmark for InMemoryDataStore Write Op

Created Benchmark for InMemoryDataStore Write Op

Created Benchmark suite for testing InMemoryDataStore write operations. The benchmark
is designed to measure efficiency of InMemoryDataStore write operations for scenarios:
 -100K Writes executed as One commit (100K items in one commit) of One outer list item with one inner list item
 -100K Writes executed as Each commit per Write (100K commits) of One outer list item with one inner list item
 -50K Writes executed as One commit (50K items in one commit) of One outer list item with two inner list items
 -50K Writes executed as Each commit per Write (50K commits) of One outer list item with two inner list items
 -10K Writes executed as One commit (10K items in one commit) of One outer list item with ten inner list items
 -10K Writes executed as Each commit per Write (10K commits) of One outer list item with ten inner list items

Benchmark suite contains of three benchmark scenarios where InMemoryDataStore is instantiated with different combinations
of executors. This will allow us to see how executor services has performance impact on DataStore write operations.

The md-sal parent pom is extended with benchmarks profile.

Change-Id: I04f6e4545445d5879d8de9785d7ba1a53ec007af
Signed-off-by: Lukas Sedlak <lsedlak@cisco.com>