Add localization mechanism for making language depending checks for text contained in a page

[tobiasstamann]

Usually the displayed text is depends on selected language in the website.
Therefore checks for plain text won't work if language setting of the page is changed.

Therefore there should be kind of a mechanism to scan for plain text, dynamic text keys that will be used to look up text depending on the language or a combination of both . It should be possible to change language via a method provided via PageObjectParent.