Strings should not contain hardcoded browser names

[daveschaefer]

There are several strings that contain the word "Firefox". But Perspectives also supports SeaMonkey, and we want to expand to support even more browsers in the future. So having these strings hard-coded is a bad UI.

We should either:

1. Remove all 'Firefox' strings and substitute with something like the word "browser"
2. Work in browser-aware detection so we can have the correct browser name shown programmatically.
3. Ohher?

If we decide to always use the word 'browser' we should document this somewhere so developers can read it.