add a .profile parser for unixy systems

[jgonggrijp]

It would be quite useful to have a command that can retrieve, add, replace, extend (prepend/append) or delete (or trim) environment variable settings from ~/.profile.

[lramati]

Given the decision to write our own .rsrc file, is this still needed?

[jgonggrijp]

I think it could still be useful.