Due to splitting the issues up some information like the category got lost. And we have those cool new Tags.

All the index.md files of the patterns should get relevant categories and tags in the yaml frontmatter. The 'pattern_cat' and 'pattern_tag' stuff can be removed as it is only a placeholder...

The 'How to Contribute' Section of the README in master should explain everything that is needed for this issue.

EDIT:
After this point is done we should remove the pattern list from the master README file.

TODO:

• Categorized all Patterns (done with adbb4ac)
• Clarify Test if we can use proper casing instead of camel case as shown in adbb4ac. EDIT: I looked it up, it should work without "", e.g. just -> Creational Patterns
  (done with 5ce932c)
• Tag all Patterns
  (partially done the with usage of tag "Java" instead of placeholder :P 5ce932c)
• Remove pattern list from master README
  (done with 5ce932c)