Refactor TS build and fix testing

This change is largely just moving files with minor tweaks to them to fix,
the rest of the commit is build process changes:

- The addons/ and test/ dirs have been moved to src/
- The build directory has been removed
- TypeScript builds are output in out/, this is where tests are run
- The demo now relies on the dist/ build which is performed as part of ./bin/build
- Addons are now shipped under the ./build directory

src/addons/attach/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "xterm.attach",
+  "main": "attach.js",
+  "private": true
+}