update NEWS and README for 2.1.0 release

[hppritcha]

NEWS needs to be updated with a lot of stuff for 2.1.0.

[jsquyres]

@hppritcha First cut on NEWS was yesterday: 4917f01. Still needs work, though -- e.g., there's a bunch of "JMS" annotations (my initials) where additional research was needed. There may also be some missing items.

[hppritcha]

related to #3058

[jsquyres]

Done!