Separate Belote and Rummy source code into packages

[marwendoukh]

Make the source code more clean by separating Belote and Rummy Classes into packages

[marwendoukh]

@mohamedamineznaidi I chose to follow this naming strategy for the xml files to make the source code more readable :

• Rummy related files should start with "rummy_"

• Belote related files should start with "belote_"