Added tests/mtsqlitetests unit test program - For developing multi-threaded Sqlite backend engine
[mtsqlitetests]  Added new class DQMtSqliteBackendEngine - Multi-thread Sqlite backend engine
tests/models => tests/testlib

AccessTests is moved from tests/sqlitetests/ to tests/testlib
Added DQBackend::supportedDriver() : Given the name of a backend engine. Return the driver supported
Added DQBackendEngine::open(QString source) : Open a database connection by a given database name
Added DQConnection::open(QString name , QString backend) : Open a database connection by a given database name
[mtsqlitetests]  Added new class DQActorBackendEngine : An actor backend engine

It is decorator of other backend engine that work as an actor. The
backend engine is able to be called by another thread through
the signal and slot mechanim in Qt
Merge commit '7f525b894535841838f5' into v0.3

Conflicts:
	tests/sqlitetests/accesstests.cpp
	tests/sqlitetests/accesstests.h
	tests/testlib/accesstests.cpp
	tests/testlib/accesstests.h
	tests/unittests/accesstests.cpp
	tests/unittests/accesstests.h