Remove hardcoded paths from acm.observables.emc

[SBouchard01]

There are still some hardcoded paths in the EMC observable classes, that should be removed and provided trough the acm.utils.paths API instead.
This would also make it easier to ensure all files are up to date.

Note

Though, I'd recommend next EMC iterations to follow the default Observable file system, as done in the BGS Observables)