remove unused code in AgentSet classes

not just unused, but could be dangerous if used -- see comment removed
from ArrayAgentSet
fix theoretical bug in new StructureParser

might affect error messages under some circumstances, not really sure
Merge pull request #401 from NetLogo/remove-unused-agentset-methods

remove unused code in AgentSet classes
upgrade to ScalaTest 2.0.M6

I forget why I got the master branch on the ScalaTest 2.0 milestone/RC
upgrade train in the first place, but nonetheless, now that we're on
it, I feel responsible that we should stay on it until we have arrived
at a stable 2.0 release

(some good news is, I've been using 2.0 milestones and snapshots on
the headless branch witp no real problems)

changes needed to get compiling/running again:
- FunSuite is now a class not a trait, so I had to adjust the
  "extends" clause of some of our test stuff, and make a few of our
  classes into traits
- due to deprecation, renamed expectResult -> assertResult everywhere
- fixed a mistaken return type for a use of withFixture
Merge pull request #428 from NetLogo/scalatest-2.0.M6-upgrade

upgrade master to ScalaTest 2.0.M6
Merge remote-tracking branch 'origin/master' into core

Conflicts:
	headless/src/main/org/nlogo/agent/World3D.java
	headless/src/test/org/nlogo/agent/World3DTests.scala
	headless/src/test/org/nlogo/api/ColorTests.scala
	headless/src/test/org/nlogo/api/VectTests.scala
	headless/src/test/org/nlogo/headless/TestImportExport.scala
	headless/src/test/org/nlogo/hubnet/mirroring/ClientWorldTests.scala
	headless/src/test/org/nlogo/hubnet/mirroring/DiffBufferTests.scala
	headless/src/test/org/nlogo/hubnet/mirroring/OverridableTests.scala
	headless/src/test/org/nlogo/lex/TokenMapperTests.scala
	headless/src/test/org/nlogo/lex/TokenizerTests.scala
	headless/src/test/org/nlogo/parse/AutoConverter1Tests.scala
	headless/src/test/org/nlogo/parse/AutoConverter2Tests.scala
	headless/src/test/org/nlogo/parse/ExpressionParserTests.scala
	headless/src/test/org/nlogo/parse/LiteralParserTests.scala
	headless/src/test/org/nlogo/plot/PlotLoaderTests.scala
	headless/src/test/org/nlogo/sdm/LoaderTests.scala
	headless/src/test/org/nlogo/sdm/ModelTests.scala
	src/test/org/nlogo/app/InfoConverterTests.scala
	src/test/org/nlogo/app/InfoFormatterTests.scala
	src/test/org/nlogo/log/LoggerTests.scala