Distinguish licenses between source and binary release

From this guide: http://www.apache.org/dev/licensing-howto.html
I understood that we have to do the following changes:
- Distinguish between the NOTICE / LICENSE file for source releases (top level directory) and binary releases ( flink-dist/src/main/flink-bin/).
- The general rule is: There has to be a NOTICE / LICENSE - entry for each bit shipped.

Therefore:
- I removed most of the contents of the top level NOTICE / LICENSE file, because the source release does not contain anything from most of the code mentioned (for example Netty, Hadoop, etc.). The only notices I left inside are for the JavaScript files, that are also contained in the source release). 
(This change assumes that we don't have to explicitly state the license/copyright of our source dependencies. I also assume that we don't have to mention Apache Hadoop or Apache Spark, from which we copied code into our codebase)

- I removed the "APPENDIX: How to apply the Apache License to your work." sections from our LICENSE file.


This pull request is meant as a suggestion that is up for discussion.