[BUG #7063] fixed representation of re-writes (list rather than map)

- to have the same key multiple times (e.g. with different arg count)
- also gather all arguments in getArgs(), to better distinguish
  between e.g. Array.toArray/1 and Array.toArray/2
- (otherwise toArray/2 gets re-written with the pattern for toArray/1)
- removed old code specific to .trim()
[BUG #7063] add test application to 2.1 migration data

- you can run 'generate.py migration' in the test project, to test migration
  data

- PLEASE DO NOT COMMIT CHANGES IN THE TEST APPLICATION AFTER A MIGRATION RUN!
  as it would ruin the test cases

- only commit the test project when you add/modify test cases for the migration
[BUG #7063] add migration.log to .gitignore