CCSABY v3 => v4; TOS => TOUAS

Upgraded Creative Commons license to new version 4.0 for newly uploaded
Catrobat programs; And: Our "Terms of Service" are now "Terms of Use and
Service" to clarify their scope.
Merge pull request #39 from Catrobat/terms_of_service_and_cc4

CCSABY v3 => v4; TOS => TOUAS