Fix #628, Fix #626!  Documentation update.

Various corrects to documentation regarding copyright dates and credits
fix typos
tweak wording
Pull in new nw extension
Small models update
Models update
Backporting fix for #161
Backport linux sbt change
Pulling in new nw extension
Update to models
Fix small error with sbt on macs
Adding extension doc for networks extension
Small update to models for release
Make extension testing ignore symlinks.

This allows extensions to have a symlinked extension directory so that
they can run their own tests.
ask-concurrent was only "concurrent" in a strange and limited sense
Correcting dictionary entry for `create-temporary-plot-pen`

Looks to me like `create-temporary-plot-pen` has been working this way since at least when the code was checked into GitHub over 3 years ago.
Merge pull request #644 from TheBizzle/5.x

Correcting dictionary entry for `create-temporary-plot-pen`
Fix typo in shapes.html
Merge pull request #648 from aochagavia/patch-1

Fix typo in shapes.html
revise Mac OS X requirements wording

hoping to avoid a misreading where users might construe it as vital
to go chasing after the latest Java