first phase of new line detection code

line changes now processed upon receiving the documents contents changed
only, which contains the position of the beginning of the change; this
should also work with undo/redo since a before selection is no longer
needed to determine line changes

there is now only a single signal emitted for line changes, which
includes the number of lines deleted and inserted; the original three
signals/slots were replaced with the new single signal/slot

the number of characters removed and added are no longer needed and so
are no longer stored; the LineDeleted line modified type value was
removed since it was not being used

not all of the possible sources of the changes have been hooked up to
rely on this new slot function; many notes have been added to the
source with some lines comments to allow compilation