[BUGFIX] PackageManager initialize() signature is incompatible (Revision 1)

PackageManagerInterface contains following method declaration::

 public function initialize(\TYPO3\Flow\Core\Bootstrap $bootstrap);

however in the PackageManager the signature is::

  public function initialize(\TYPO3\Flow\Core\Bootstrap $bootstrap,
    $packagesBasePath = FLOW_PATH_PACKAGES,
    $packageStatesPathAndFilename = '')

This will create a fatal error on some versions of php and when running
unit tests on hhvm (of CMS), see
http://php.net/manual/en/language.oop5.interfaces.php:

"The class implementing the interface must use the exact same method
signatures as are defined in the interface. Not doing so will result
in a fatal error."

This change updates the method signature of the PackageManager to be in
line with the interface.

Change-Id: I94cf40fb788861f2e4c9e656bea57a0ff2354113
Fixes: #56409
Releases: master, 2.1
Revision-Id: 6c4fbd6d2f2da6d196ddf926c1b60c0152912e5e