app blueprint: don't trim whitespace from diffs

With the current setting, editorconfig-compliant editors will remove trailing whitespace on `.diff` files - which means that solving a conflict with the `e` option (to edit the patch to be applied) becomes impractical.
Use AST transforms for adding new routes and resources.

This uses the following micro lib
https://github.com/abuiles/ember-router-generator, we still need
support for deletions.

A full list of scenarios can be seen in the following test file
https://github.com/abuiles/ember-router-generator/blob/master/tests/generator-test.js
Merge pull request #2748 from abuiles/apply-ast-transforms-to-router

Use AST transforms for adding new routes and resources + path option
Remove routes and resources via ember-router-generator.
Merge pull request #2750 from abuiles/replace-route-removal-with-ast-transforms

Remove routes and resources via ember-router-generator.
Document changes from #2748
Merge pull request #2734 from renato-zannon/patch-1

app blueprint: don't trim whitespace from diffs