Much overhauling...
Tidy up and correct a couple things...
Beginnings of new selection system.

PRESENTLY WORKING:
* `NoSelection * (BoL, MoL, EoL) * (FirstLine, MiddleLine, LastLine)`
* `SingleLineBlock * (FirstLine, MiddleLine, LastLine)`
* `MultiLineBlock * (FirstLines, MiddleLines, LastLines)`

Basically, both indent/unindent have problems with variations of mid-line-selection.
Tidy up a bit...