fix Prims.sort to be nondestructive
add `reverse` prim (for both lists and strings)

tests for this already exist in the language tests.  it's also used in
some tests whose main purpose is to test other things, so it's good to
have.
fix bug where `sort` mutated input agentset
minor cleanup
Merge pull request #81 from NetLogo/make-sort-nondestructive

fix bug where `sort` mutated its input list
revert mysterious import change

@TheBizzle doesn't remember why this was included in
47be69d4144a74f7b01e92fb48423cd87f9dc4c0, so I'm reverting.  if it ends
up needing to be reinstated for some reason neither of us can
currently fathom, it should be commented.
Introducing Benchmarker 1.0
Adding version number of JS engine to benchmark

It just makes sense to include version numbers of external libraries
into the benchmarks, since changing version numbers can change speed.
Minor package-pushing (refactoring)
Pumping up the private sector
Refactoring trait to use a type variable

It's just easier to deal with unification/parameterization this way
Adding SpiderMonkey support
Turning on Nashorn for benchmarking

(cherry picked from commit 54496f6f602b177b0e0a1168aaf55497a9b638bd)