and merges in subsequent transactions indiscriminately until it's told to stop.
It also gives the last transaction in its child list a chance to merge the
next transaction.
All this is in support of complex transactions that result in text insertion
being able to collapse into a single undoable event.
Also improved tracking of bogus content node used when document is empty.
added nsEditProperty
beginning of implementation for SetTextProperties. Currently, it only works if the selection is entirely within a single text node. Currently only
supports bold and italic (mapped to ctrl-b and ctrl-i for testing purposes.)
changed a bunch of interfaces to make things easier, like CreateElement now returns (as an out-param) the element created.
* added DeleteSelection to editor. Doesn't work very well yet because selection is giving me random offsets into text content.
* lots of work in the various transactions.
