Clean up LICENSE and NOTICE files

This commit is from @uce.

1. Added LICENSE and NOTICE files to the source tree
=> we now have two files, one for the source, one for the dist

2. Renamed LICENSE.txt and NOTICE.txt without the .txt 
=> This seems to be the common naming.

3. Removed swt-visualization project, because it used LGPL 2.1 dependencies and nobody really uses it. (We do not support it)

5. Removed the notices about the usage of other Apache licensed SW, because I am not sure if we need it