[INTERNAL] cleanup and refactor CachedMzML
[TEST] add test to CachedMzML
[INTERNAL] move CachedMzML to FORMAT
[FIX] additional fixes

- [TEST] test error conditions
- [TEST] make test faster
- fix header guards
- remove MAGIC_NUMBER macro
Merge pull request #680 from hroest/feature/CachedMzML_fixes

[INTERNAL] Feature/CachedMzML fixes