JB2008 DataLoaders implementation

Define Data and DataLoader classes for JB2008's input files SOLFSMY and DTC. Code based on CssiSpaceWeatherData and its associated DataLoader. A LineReader has been defined, and might be used in CssiSpaceWeatherDataLoader, to limit duplication. Define basics tests to check file parsing and coherent behaviour with Orekit's design. All tests are passed, with validation. Duplication is still present.