make initializer create the homepage rather than a generic page

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | (probably not yet as other bundles adjustments not merged yet)
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

There is a BC break in https://github.com/doctrine/DoctrinePHPCRBundle/pull/97 - but actually, putting a Generic document at /cms/simple is pointless. created an initializer for a basic homepage Page.

/cc @dantleech