Integration build supports modularized scala.

After this is merged, scala/scala#2855 should validate for IDE integration.
I also cleaned up the build script a bit.
The main change is:

```diff
+      "set (libraryDependencies in cacheSub         ) ~= { ld => ld map { case dep if (dep.organization == \"org.scala-lang.modules\") => dep cross CrossVersion.fullMapped(_ => \"$SCALA_BINARY_VERSION\") case dep => dep } }"\
+      "set (libraryDependencies in compilePersistSub) ~= { ld => ld map { case dep if (dep.organization == \"org.scala-tools.sbinary\") && (dep.name == \"sbinary\") => dep.copy(revision = (dep.revision + \"-SNAPSHOT\")) case dep if (dep.organization == \"org.scala-lang.modules\") => dep cross CrossVersion.fullMapped(_ => \"$SCALA_BINARY_VERSION\") case dep => dep } }"\
+      "set (libraryDependencies in mainSub          ) ~= { ld => ld map { case dep if (dep.organization == \"org.scala-lang.modules\") => dep cross CrossVersion.fullMapped(_ => \"$SCALA_BINARY_VERSION\") case dep => dep } }"\
+      "set (libraryDependencies in processSub       ) ~= { ld => ld map { case dep if (dep.organization == \"org.scala-lang.modules\") => dep cross CrossVersion.fullMapped(_ => \"$SCALA_BINARY_VERSION\") case dep => dep } }"\
```

I tested these changes manually against scala/scala#2855 (master) and scala/scala#2876 (2.10.x).
Log files here: https://gist.github.com/adriaanm/6361216
(the result against #2855 was using a slightly older commit, but very little has changed since in the PR)

review by @dragos