* Add annotations to files under core/events
* Add annotations to files under core/interfaces
* Add annotations to files under core/keyboard_nav
* Add annotations to files under core/renderers
* Add annotations to files under core/serialization
* Add annotations to files under core/theme
* Add annotations to files under core/toolbox
* Add annotations to files under core/utils
* Add annotations to files under core
* Add getSelected/setSelected to core/common.js
* Migrate core to use Blockly.common.getSelected/setSelected instead of Blockly.selected
* Migrate demos to use Blockly.common.getSelected/setSelected instead of Blockly.selected
* Remove Blockly.selected
* Use variable instead of calling common.getSelected() multiple times
* Add accessor for selected on Blockly
* Add renaming record for Blockly.selected -> Blockly.common.getSelected/setSelected