Tests: Add unit tests for CSV import

Add a new test class for testing the import functionality. Currently
it's only covers some test cases for the CSV import.

Since the function to test here (DBBrowserDB::decodeCSV) is part of the
DBBrowserDB class, that class has a reference to the main window and the
main window basically depends on the entire rest of the project the
makefile grew quite a bit unfortunately.

src/tests/testsqlobjects.cpp

@@ -249,6 +249,3 @@ void TestTable::createTableWithNotLikeConstraint()
     QVERIFY(tab.fields().at(5)->check() == "value6 NOT BETWEEN 1 AND 100");
     QVERIFY(tab.fields().at(6)->check() == "NOT EXISTS ( 1 )");
 }
-
-QTEST_MAIN(TestTable)
-//#include "testsqlobjects.moc"