The Buffer::dispatch() patch.

The Buffer::dispatch() patch.

This patch enhances the Buffer::dispatch() method to make it a full-fledged
member of the dispatch sequence. The most immediate payoff is that LFUNs that
are handled in Buffer::dispatch() can be used from the command line.

We make better use of the DispatchResult object and return error information
through it, rather than using return values. (This was JMarc's suggestion.) We
also introduce a  corresponding Buffer::getStatus() method, and modify
BufferView::getStatus() to return a flag indicating whether a decision has been
made, as is already done in some other cases.

Finally, some LFUNs are moved to Buffer::dispatch(), including LFUN_BUFFER_PRINT.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@29125 a592a061-630c-0410-9148-cb99ea01b6c8