Implements #710
Conflicts:
	src/main/java/com/jaeksoft/searchlib/index/IndexLucene.java
	src/main/java/com/jaeksoft/searchlib/index/WriterLocal.java
	src/main/java/com/jaeksoft/searchlib/scheduler/task/TaskDeleteQuery.java
	src/main/java/com/jaeksoft/searchlib/webservice/document/DocumentImpl.java
Implements #710. Adding new unit tests.
Conflicts:
	src/main/java/com/jaeksoft/searchlib/Client.java
	src/main/java/com/jaeksoft/searchlib/index/IndexLucene.java
	src/main/java/com/jaeksoft/searchlib/index/WriterInterface.java
	src/main/java/com/jaeksoft/searchlib/index/WriterLocal.java
	src/main/java/com/jaeksoft/searchlib/webservice/query/document/DocumentsImpl.java
Merge pull request #722 from emmanuel-keller/1.6

Implements #710