replace old StructureParser with parser-combinator-based rewrite
Merge commit '378776800b221f22aa8a6355f2b11a7bfc4b3de0' into scala-2.10

Conflicts:
	headless/src/main/org/nlogo/compiler/StructureParser.scala
	headless/src/test/org/nlogo/compiler/AutoConverter1Tests.scala
	headless/src/test/org/nlogo/compiler/AutoConverter2Tests.scala
	headless/src/test/org/nlogo/compiler/StructureParserTests.scala
work around parser combinator regression on Scala 2.10

where Workspaces weren't being GC'ed, causing lots of test failures
(TestHalt failed outright, and lots of other stuff would fail randomly
once we ran out of heap due to un-GC'ed stuff piling up)