refactored retrieving data. now the application returns the string instead of saving the result into file

adding input, radius, radiustype into JSON export structure, introducing OutputData such as the structure to represent values that should be exported

Refactored to Spring Boot

See merge request !1

refactoring initFxml method, adding executor shutdown after main stage is closed (i.e. application is closed)

data from MAST are now available in result window. Introducing /data folder for keeping data from catalogues
deleting k2_ffi, kepler_ffi and swift_uvot from MAST tables as they are not applicable

added error handling for Vizier part. Added "unlimited" parameter, so it won't limit user from downloading data with more than 50k rows.

Introducing Result Window with working table and columns showup. TODO: fill results with data

adding cds.savot parser, this is still in analytical phase as VOTable standards implemented in Vizier/Simbad/MAST differ