feat(gen): add grunt-ngdoc comments
feat(build): replace grunt-bower-install with grunt-wiredep

Because its better. Really because its the same thing with its name
changed
fix(app): app is installed at appPath location

appPath was only being used for some things and the rest were all going
into `app/`. This fixes that all files are placed in the correct appPath
location and usemin paths are correct as well.