Fix issue #2298. Do not copy record during query processing.
Merge branch 'develop' into orientdb-2298

Conflicts:
	core/src/main/java/com/orientechnologies/orient/core/sql/OCommandExecutorSQLInsert.java
	core/src/main/java/com/orientechnologies/orient/core/sql/OCommandExecutorSQLSelect.java
	core/src/main/java/com/orientechnologies/orient/core/sql/OCommandExecutorSQLTraverse.java
Minor: add comments to quickly turn on debugging
Introduced ConcurrentTestHelper
Improve concurrent test
Merge branch 'develop' into orientdb-2298