upgrade ScalaTest to match what scala-2.11 branch has

we might as well, since it will help reduce merge conflicts between
that branch and this one (headless).

cherry-picked from 2.11 branch:
(cherry picked from commit 0b5d54dfe1720356b661a1f7afba607a62e75991)
(cherry picked from commit 4391792cff94c9ed8a1ffe174357c6cd447a16b2)
retrieveManaged/lib_managed no longer needed

now that our auxiliary scripts like benches.scala and profiles.scala
run through sbt instead of doing their own classpath-building, we
don't need to copy our managed jars into lib_managed anymore, we can
just go with the default sbt 0.10+ behavior of leaving them in
~/.ivy2/cache
fix up incorrectly rejiggered link-length prim

happened to notice this while doing something else. nbd, but the
bytecode generator can do a better job when this is right
bytecode generator: beef up MethodSelectorTests a little
give all report/report_* methods explicit return types

the main impetus for this was that in Scala 2.11, if you override
an AnyRef-returning method the compiler will no longer infer a more
specific return type if it can. the more specific return types are
valuable because the bytecode generator can use them.

committing this even for use with 2.10 because it seems like a
code improvement, actually; better not to rely on type inference
for something so crucial as the return types of these methods.

the benchmark dumps change a little, for the better, because some
int-to-double conversions are now happening before bytecode generation
fix bad dependency in test
fix bad dependency in test, the right way this time
rename a test to follow naming convention
beef up MockSuiteTests

I thought I had spotted a bug, but it seems I was wrong.  good to have
the additional tests, regardless.
have Travis notify #netlogo on IRC
redo headless.lang tests to use fixture.FunSuite

instead of gross mutable stuff

the added "fixture =>" and "implicit fixture =>" stuff is kind of
noisy, but better than resorting to mutability IMO.

off in headless.model, Josh Cough chose to stash the fixture
in a DynamicVariable to avoid the extra noise. it's something
we could consider.

also rename stuff in headless.lang (sorry part of same commit; I got
all tangled up in git)
tighten up nightly.sh

`all` and `extensions` are about the same now, so no need to do
`extensions` separately anymore. also renumber the phases now
that headless is its own line of development and rapidly drifting
out of sync with 5.0.x and master anyway
refactor/DRY in headless.lang.Fixture
oops, fix regression in headless.lang
make Evaluator.runCompiledCommands/Reporter respect owner.kind

this is a bug or missing feature of long standing, only uncovered now
that I'm about to change headless.lang.Fixture to use these methods
minor code improvement in headless.lang
minor code improvement to headless.lang.Parser

also, sample-scala's tests.txt had an inconsistent test format, which
the improvement caught
code improvement in headless.lang.Fixture

DRY testCommandCompileError out of existence
put headless.lang.ParserTests in its own file
minor code improvement in headless.lang.ParserTests