This gasctionsignal allows us a bit more control over how the paste will
be interprited. For example, we can allow/disallow smart pasting of lines
(lines with trailing \n such as those from `yy` in vim mode).

It also allows us to specifiy if they should happen before or after
the current cursor.

If place_cursor_at_original is FALSE, then we will move the insertion
cursor to the beginning of the pasted text (which may be on a different
line if smart_lines is TRUE).