Add control modifier select mode unit tets.  Exclusive failing.
Test caret position after exiting selection mode.
Fix exclusive selection in select mode.
Add standard copy/paste/delete shortcuts to select mode; previously inserted control chars.
Fix editor ops for Ctrl+Home and Ctrl+End.
Permit exclusive selection to extend to end of buffer.
Clarify comment preceding inclusive adjustment.
Add Shift+Left and Ctrl+Shift tests.  Obey virtual edit settings on exit from select mode.