#11 Move test and exmaple classes of Xpregel (in org.scalegraph.xpregel) to test page and suffix the class name with XPregel

[Charuwat]

Move test and exmaple classes of Xpregel (in org.scalegraph.xpregel) to test page and suffix the class name with XPregel.

P.S.
1 Please don't forgot the change class name in the code.
2. Please also check that those classes can be successfully compiled