Backport Fix #1154: Add @JSExportDescendentClasses (exports subclass ctors)

Backport:
- Fix stub project specifically for 0.5.x.
- Add method `decodedFullName` originally introduced in
  698d69814eb250656f076eda494397e649bb0f78.
- Adapt package name in ExportsTest for 0.5.x:
  scala.scalajs.{testsuite => test}.jsinterop

(cherry picked from commit b128e480ec8adc6bf1b095de37da725aeebe1c62)

Conflicts:

	stubs/src/main/scala/scala/scalajs/js/annotation/ExportAnnotations.scala
Backport js.Dynamic.newInstance returns Object with Dynamic.

Instead of just Dynamic.

(cherry picked from commit dad0941befaf0663cdcfdf520a9ba1eed19d551e)
Backport Mark js.WrappedDict as inlineable, and override its keys method.

(cherry picked from commit cee83a8e13d5f99d61370335d9a5f0d8556eea6d)
Backport Improve the implementation of Long.to{Binary,Hex,Octal}String.

It does not use Formatter anymore, and does not require to drop
the leading 0's after the fact.

(cherry picked from commit 9e43ed89ea3c33e4ecdb9753879b25605a42ebd3)

Conflicts:

	javalanglib/src/main/scala/java/lang/Long.scala
Backport Fix unit test for DataInputStream.readLong().

It's not good to give Longs to Jasmine for comparisons, because
they are converted to Doubles.

(cherry picked from commit b692d0be4bcbbb9704e11a84c0f2393f6684dc9f)
Backport Fix #1169: Make IR printer print cases of match tree nicely

It now looks like this:

    match (x1) {
      case 1 | 2 | 3:
        mod:s_Predef$.println__O__V("low");
      case 4:
        mod:s_Predef$.println__O__V("four");
      default:
        mod:s_Predef$.println__O__V("other");
    }

(cherry picked from commit 0d6504b872d191e600ebf638e5fad0fae6db23ce)

Conflicts:

	ir/src/main/scala/scala/scalajs/ir/Printers.scala
Backport Avoid crashing for classpath elements that do not exists on the file system.

Added DummyVersion constant value, exists() to detect file that does not exists and getDummyVersion to provide a string version for a dummy file.
Implemented DummyVersion and isDummy in physical and node file systems.
Added simple ClasspathElementsTraverser tests using the PhysicalFileSystem.

(cherry picked from commit 76df98df86465cf7d1663226b3d6d1c20c33d006)

Conflicts:

	tools/shared/src/main/scala/scala/scalajs/tools/classpath/builder/ClasspathElementsTraverser.scala
Backport Fix a few typos in scala.scalajs.js package object docs

(cherry picked from commit 6689fef40aa84062bcb37da652cca88f07e04404)
Backport Fix #1191: Reset caseaccessor flag on export forwarders

(cherry picked from commit 2310223109bf2c81c255c82b32b94ac435c9acb2)
Backport Fix #1171: Split: Sometimes remove leading empty match

The conditions were determined experimentally since the JavaDoc is
note precise enough.

(cherry picked from commit cba58ff2c58ce916ebd4df942612f8538ea6bb70)
Backport Fix #364 for good: remove magical Rhino top-level package objects.

Instead of hard-coding a list of known problematic top-level
package names, we detect what needs to be removed by listing
the properties in the Packages object.

Backport: In 0.5.x, the LiveConnect classes were removed before
loading env.js (unlike 0.6.x). The backport leaves these steps in the
order they were in 0.5.x.

(cherry picked from commit 856029644aa01c16b2df0c7e696615e956b55eec)

Conflicts:

	sbt-plugin/src/main/scala/scala/scalajs/sbtplugin/env/rhino/RhinoJSEnv.scala
Backport Add replace and deleteCharAt methods to StringBuilder and StringBuffer

(cherry picked from commit 20973bc986ccaf78082e00dd0fd7380a9c630cac)
Backport Use a Traverser in JSASTTest instead of a Transformer.

(cherry picked from commit 4752db29e17d5960b18b4aab73c34f83b01a486d)
Backport Using a Transformer in scalajsp is overkill.

It only needs to transform the top-level node, so a simple
function is enough.

(cherry picked from commit 47408a5f65e1243dda35449be5117bce102ef429)

Conflicts:

	cli/src/main/scala/scala/scalajs/cli/Scalajsp.scala
Backport Fix #1206: Update to sbt 0.13.6

Also fix the sbt version for the sbt-plugin-test build.

(cherry picked from commit 11c29f9c138a700657258617e3ac233a1fa9bbe7)