Add Apache License to all files

[JonathanArns]

Closes #15

[powibol]

Thank you for this pull request! In order to merge it, we would like to ask you to apply the following updates and extensions:

• Since the Scotty Window Processor is not a project of the ASF, the license note in each file should be as stated in the bottom of this page: http://www.apache.org/licenses/LICENSE-2.0
• The copyright owner should be "TU-Berlin DIMA" (See https://github.com/emmalanguage/emma/blob/master/emma-language/pom.xml as example)
• There should also be a LICENSE file in the root directory which contains a copy of the Apache License.
• We believe that we do NOT need to add third party licenses at the moment (no notice file), because the repostitory does not contain third party projects. However, feel free to make another suggestion if you are more experienced with licensing than we are ;)

Thank you very much in advance for your work!