Convert batch wizard to use new slider/text control

This reduced code line count rather dramatically, which is great since
that form is so dense.
Convert monochrome conversion form to use new slider/text control
Update a number of tools to provide more accurate output for selections

Specifically, representing the preview accurately for any operation that
requires a radius and is being applied to a selection.
Convert box blur to use new slider/text custom control

For interest's sake: every time I convert a tool window to using the new
control, 4kb is shaved off the compiled .exe.  Considering that
PhotoDemon has some 60 tool dialogs, that's some big savings.