renamed default app from 'myApp' to 'frontend'

[klemens_u]

Hello devs,

I renamed the default app from 'myApp' to the symfony default name
'frontend' to be consistent with tutorials and other projects.

This has the following impacts:

o) For all symfony cli command you have to use 'frontend' now
Example: php symfony doctrine:build-all-reload --force frontend
o) The url for the dev environment is now http://ullright/frontend_dev.php

:-) Klemens