This commit adds support for showing a preview of long lines. While the
default still remains as completely suppressing the entire line, this
new functionality will show the first N graphemes of a matching line,
including the number of matches that are suppressed.
This was unfortunately a fairly invasive change to the printer that
required a bit of refactoring. On the bright side, the single line
and multi-line coloring are now more unified than they were before.
Closes#1078
ece1f50cfe