Add test for piece distribution options in XML MBDS reader.

IO/XML/Testing/Cxx/CMakeLists.txt

...ML/Testing/Cxx/TestXMLCompositeDataReaderDistribution.cxx

Testing/Data/distTest.vtm.md5

Testing/Data/distTest_0_0.vtp.md5

Testing/Data/distTest_1_0.vtp.md5

Testing/Data/distTest_2_0.vtp.md5

Testing/Data/distTest_3_0.vtp.md5

Testing/Data/distTest_4_0.vtp.md5

Testing/Data/distTest_5_0.vtp.md5

Testing/Data/distTest_6_0.vtp.md5

Testing/Data/distTest_7_0.vtp.md5

Testing/Data/distTest_8_0.vtp.md5

Testing/Data/distTest_9_0.vtp.md5