Change logic behind "check all" selection to RT events.

This changes the logic behind how events are selected for mass
classification when the check all box is selected. Currently,
the logic selects all events within a specific row regardless
of whether they have already been classified or not with the
side effect of reclassifying already previously classified events.

e.g. If a row having 100 RT events and 200 classified events will
include a check all box to mass classify the 100 RT events. The
current logic will classify all 300 events.

This patch also resolves the "Too many events in current selection"
UI error by not counting previously classified events.