[TEST] add test for TraML file

- TraMLFile should be able to store a (valid) minimal example of a TraML
  file and read it again.
[FIX] ensure valid TraML file is written by not outputting a double equal to numeric limits
[FIX,PYOPENMS] add operators to TargetedExperiment
[FIX] add inequality operator
[TEST,PYOPENMS] add test
Merge pull request #1037 from hroest/fix/TraMLLoadStore

Fix/ TraML load/store