issue1622: metricsview kerning, charview multichar trailing /.

allow trailing slash in charview, don't crash when altering kerning in
metricsview and there are multiple kern pairs visible with the current
value. mv: update other kern pairs when changing the current kern pair.
cleanup
comment
Merge pull request #1697 from fontforge/monkeyiq/2014/aug/1622p1

issue1622: metricsview kerning, charview multichar trailing /.