[BUGFIX] Stabilize "Consistent escaping behavior" core migration
This tweaks the ``TYPO3.Fluid-20150214130800`` core migration to always
include the ViewHelper file before adding the ``escapeOutput`` flag.
Besides it now uses the ``PhpAnalyzer`` class to extract the ViewHelper
When executing core migrations the class loader might not be initialized
yet. This makes sure the ViewHelpers can be adjusted anyways.
Releases: master, 3.0