Added ido-invoke options to open in another window / frame

From gist (referenced in commit) found on emacswiki page for `ido`.  Allow to open from ido in:
- open in other window
- open in other frame
No issue, I was just trying to be consistent with the default vim command line bindings (-o), but in that case, I guess vertical should be C-S-o.  If I was basing off of the `<C-w>` commands, it would be `s` and `v`.  Where does the `b` come from, is it original to spacemacs? 

Will update the PR.