several fixes to JVET-L0428 related code additions, editorial fixes
fixed encapsulation in previous commit, fixed initCULevel() for the case where JVET_L0428_DQP_SEP_TREE is not defined, corrected some conditions in previous commit (especially against null-pointers), replaced remaining tabs in code with spaces, corrected some indentations in xGetPredValDc() and coding_tree_unit(), removed some trailing whitespace in IntraPrediction.cpp