Moved global PAGE_* to Profile class (#5500)

Moved global PAGE_* to Profile class (#5500)

* Rewrites:
- moved PAGE_* to Friendica\Model\Profile class

* Fixed more rewrites from plain (global namespace) PAGE_* to Friendica\Models\Profile class

* CR request:
- moved all PAGE_* constants to Friendica\Model\Contact class
- fixed all references of both classes

* CR request:
- moved ACCOUNT_TYPE_* constants from boot.php to Contact::ACCOUNT_TYPE_*

* Just copy-pasted this code from boot.php, needs to be changed to `const ACCOUNT_TYPE_FOO = x;`

* Ops, melting brain cells here ... :-/