emacs: more flexible and consistent tagging operations

[Austin Clements]

The whole series LGTM.

Quoth Dmitry Kurochkin on Jan 30 at  9:33 am:
> Changes:
> 
> v3:
> 
> * merged 3 `notmuch-show-tag-all'-related patches into one
> 
> * add patch to clean up tagging function argument names
> 
> * fix other comments from Austin's reviews [5,6]
> 
> v2:
> 
> * add patch to remove "No tags given" error from `notmuch-tag' as
>   suggested by Austin in [1]
> 
> * split patch 3 in two (search and show) for easier review
> 
> * add patch with NEWS entry
> 
> * rename `notmuch-{search,show}-operate-all' to
>   `notmuch-{search,show}-tag-all'
> 
> * fix other comments from Austin's reviews [2,3,4]
> 
> Regards,
>   Dmitry
> 
> [1] id:"20120129231650.GK17991 at mit.edu"
> [2] id:"20120129225710.GG17991 at mit.edu"
> [3] id:"20120129230229.GI17991 at mit.edu"
> [4] id:"20120129231120.GJ17991 at mit.edu"
> [5] id:"20120130044806.GM17991 at mit.edu"
> [6] id:"20120130050402.GP17991 at mit.edu"