Fix page template configuration

At first: Bear with me :) This is my first PR

I noticed some troubles in workspace-mode, so I have rewritten some parts in the methods: getPageTemplateConfiguration() and getPageFlexFormSource().
For an easier handling I have added to Functions:
- getPage($pageUid), which returns the right page array depending on workspace-mode
- getPageParent($page), which returns the right parent page

Workspaces currently works only in single-domain setups starting in a low page level.
I have written a small bugfix for the extbase core that will fix this (http://forge.typo3.org/issues/49437)

kind regards
heiko