Dependency checker for pagepackages (#47)

* New method for osw.data.mining.RegExPatternExtended

* Removed redundant and deprecated function call

* Added dependency checker for PagePackages

* Including check of dependencies for Items and Files

* Fixing recursive dependency check + Renaming of functions for readability + Docstrings added

* Fix: If no new missing pages were found, no missing pages would be labeled

Enh: Removing unneeded parameters

* hotfix for pre_suffix determination

(in case the "omit slot suffix" for main slot is active)

* Hotfix of Validation Error for LoadEntityParam

* reformatting

Author: LukasGold