Project sanity check (#76)

* tslint: CRLF -> LF

* gitignore more build artifacts

* Add proposed .editorconfig

* Allow for "clean" builds

src/ts/generated/ content is still required (sprites.ts,
gamepad-mappings.ts), but src/scripts is not.

* Add --sprites option to production build

* Add note about sprites to README

tsconfig.tools.json

@@ -0,0 +1,6 @@
+{
+  "extends": "./tsconfig.json",
+  "files": [
+    "src/ts/tools/create-sprites.ts"
+  ]
+}