Arguments for `where`

[jacobobq]

Problem description

It could be nice to be able to use where or bt with an optional number argument to show only the top number stack frames because I don't usually care about frame #175 from puma. It could rule even more to be able to only print frames up until a certain file name comes up by way of where path/to/file

Expected behavior

When bt 10 is input, only the first 10 frames of the stack are in the output.
When where path/to/file is input, frames are shown only until the first occurrence of path/to/file.