Added disposed property to blocks (for use in unit tests).
Added disposed property to blocks (for use in unit tests).

google/blockly,rachel-fenichel/blockly,google/blockly,rachel-fenichel/blockly,mark-friedman/blockly,picklesrus/blockly,google/blockly,mark-friedman/blockly,google/blockly,mark-friedman/blockly,picklesrus/blockly,mark-friedman/blockly,rachel-fenichel/blockly,google/blockly,mark-friedman/blockly,rachel-fenichel/blockly,google/blockly,rachel-fenichel/blockly,google/blockly,mark-friedman/blockly,rachel-fenichel/blockly,rachel-fenichel/blockly,picklesrus/blockly