QueryStatement interface should have a setStringContains() method

The QueryStatement interface has two methods to set a string value: setString() and setStringLike(). They differ in how the string is escaped.

The escaping for CONTAINS in the CMIS query language is different to those two. At the moment, the application has to this escaping. It would be nice, if a method setStringContains() could do a spec compliant escaping automatically.