Allow keys to be specified using globs/pattern matching

[zgramana]

We have some rather large and deeply nested expvars. As a user, I would love to use globs instead of commands like this:

./expvarmon -vars="cb.ops.Write(raw).count,cb.ops.Write(raw).p99,cb.ops.Write(raw).p95,cb.ops.Write(raw).p90,cb.ops.Write(raw).p75,cb.ops.Write(raw).p50,cb.ops.Write(raw).p25"

For example, it would be great to instead be able to simply type:

./expvarmon  -vars="cb.ops.Write(raw).*"

or even

./expvarmon  -vars="cb.ops.*"

[divan]

Hi Zachary. Current design is based on fixed list of vars names, UI is being constructed before vars are fetched.
Refactoring to support wildcards is probably viable, but it adds a number of complications that should be addressed and solved right. UI should be (re)arranged on each json parse, service downtimes should be handled differenly (if UI depends on each JSON data blob), etc.

I'll think about it, but not promising a quick solution. Meanwhile, if you're up to solve this gracefully, PR is always welcome.