* Fix error conditions for setParent #4989
* Error now thrown when calling `a.setParent(b)` on non-null b if the output/previous connection of a is not connected to an input/next connection of b without removing block from old parent's child list.
* Commented out error for when calling `a.setParent(null)` if a is connected to superior block.
* Adjusted comment to reflect that blocks were no longer being disconnected in this method.
* Also changed == to === per #4924 (`newParent` and `this.parentBlock_` must both be instances of `Blockly.Block`).
* Fix error conditions for setParent #4989
* Error now thrown when calling `a.setParent(b)` on non-null b if the output/previous connection of a is not connected to an input/next connection of b without removing block from old parent's child list.
* Error now thrown when calling `a.setParent(null)` if a is connected to a superior block.
* Adjusted comment to reflect that blocks were no longer being disconnected in this method.
* Also changed == to === per #4924 (`newParent` and `this.parentBlock_` must both be instances of `Blockly.Block`).
* Fix error conditions for setParent #4989
* Error now thrown when calling `a.setParent(b)` on non-null b if the output/previous connection of a is not connected to an input/next connection of b without removing block from old parent's child list.
* Commented out error for when calling `a.setParent(null)` if a is connected to superior block.
* Adjusted comment to reflect that blocks were no longer being disconnected in this method.
* Also changed == to === per google#4924 (`newParent` and `this.parentBlock_` must both be instances of `Blockly.Block`).
* Fixed lint errors.
* Fix error conditions for setParent google#4989
* Error now thrown when calling `a.setParent(b)` on non-null b if the output/previous connection of a is not connected to an input/next connection of b without removing block from old parent's child list.
* Commented out error for when calling `a.setParent(null)` if a is connected to superior block.
* Adjusted comment to reflect that blocks were no longer being disconnected in this method.
* Also changed == to === per google#4924 (`newParent` and `this.parentBlock_` must both be instances of `Blockly.Block`).
* Fixed lint errors.
* Adjusted comment.
* Removed unnecessary set to null/added tests
* One is failing (commented out), will investigate later
* Lint fix
* Removed failing test that correctly fails
* Update comments to conform to style guide
Capitalize first letter, period at end
* Now throws error for getField/getFieldValue/setFieldValue if provided name is not a string
* Changed error to more specific TypeError
* Type checking and error message moved up to getField
* Tests added/modified to check that non-string types for field names produce type errors
* Added tests for getting/setting field (values) when names are not supplied and test for getting a field value, setting it to a new value, and getting it again.
* Added more user-friendly error message for setFieldValue telling the developer that he/she is missing the name rather than Field "undefined" not found.
* Fixed lint error by removing trailing space
* Added tests for getting/setting field (values) when names are not supplied and test for getting a field value, setting it to a new value, and getting it again.
* Added more user-friendly error message for setFieldValue telling the developer that he/she is missing the name rather than Field "undefined" not found.
* introduce IDraggable interface
* Add parameter to drag methods in IDragTarget
* combines bubble/drag methods on IDragTarget and IDeleteArea to take an IDraggable element
