Adding warning on duplicate JSON block definition.
Adding warning on duplicate JSON block definition.

griffpatch/scratch-blocks,picklesrus/blockly,trinketapp/blockly,lzairdking/blockly,griffpatch/scratch-blocks,nickmain/blockly,LLK/scratch-blocks,groklearning/blockly,rachel-fenichel/blockly,hkoi/blockly,carlosperate/blockly,google/blockly,twodee/blockly,jano42/blockly,twodee/blockly,InspectorWidget/blockly,mark-friedman/blockly,rachel-fenichel/blockly,jstnhuang/blockly,griffpatch/scratch-blocks,lzairdking/blockly,gengshenghong/scratch-blocks,nickmain/blockly,rachel-fenichel/blockly,markocelan/blockly-minecraft,carlosperate/blockly,groklearning/blockly,InspectorWidget/blockly,jstnhuang/blockly,LLK/scratch-blocks,google/blockly,joshlory/blockly,trinketapp/blockly,rachel-fenichel/blockly,jstnhuang/blockly,mark-friedman/blockly,gengshenghong/scratch-blocks,twodee/blockly,trodi/blockly,groklearning/blockly,picklesrus/blockly,lzairdking/blockly,LLK/scratch-blocks,LLK/scratch-blocks,google/blockly,mark-friedman/blockly,joshlory/blockly,mark-friedman/blockly,jano42/blockly,trodi/blockly,markocelan/blockly-minecraft,twodee/blockly,google/blockly-devtools,google/blockly-devtools,InspectorWidget/blockly,markocelan/blockly-minecraft,trinketapp/blockly,google/blockly,google/blockly,picklesrus/blockly,joshlory/blockly,LLK/scratch-blocks,gengshenghong/scratch-blocks,google/blockly,groklearning/blockly,gengshenghong/scratch-blocks,google/blockly,trodi/blockly,rachel-fenichel/blockly,trodi/blockly,hkoi/blockly,griffpatch/scratch-blocks,nickmain/blockly,rachel-fenichel/blockly,trinketapp/blockly,twodee/blockly,mark-friedman/blockly,twodee/blockly,carlosperate/blockly,nickmain/blockly,jano42/blockly,carlosperate/blockly,nickmain/blockly,mark-friedman/blockly,nickmain/blockly,rachel-fenichel/blockly,jstnhuang/blockly,gengshenghong/scratch-blocks,lzairdking/blockly,markocelan/blockly-minecraft,hkoi/blockly,griffpatch/scratch-blocks,jano42/blockly