* Changed splice to check all elements about to be inserted are allowed before inserting any of them so that catching an exception leaves you in a sane state
* Fixed the order of execution of parent class constructors in ve.dm.LeafNode and ve.dm.TwigNode so that canHaveChildren and canHaveGrandchildren produce correct values and added tests to ensure these methods are correctly inherited in subclasses
* Added tests that check for exceptions when adding nodes that can have children to nodes that can not have grandchildren
* Added test that check for events being emitted before and after splicing, including that beforeSplice should be emitted even in cases where a splice fails and throws an exception because the nodes are incompatible (but afterSplice is not called in this case) since beforeSplice might modify the nodes in some way before the compatibility tests are run
Change-Id: Id12aea995a42c26ff63a74ae3d31f2bf455759e3
