Basic generic filter.oiexp 11

[buthanoid]

Related to https://github.com/JMMC-OpenDev/oiexplorer/issues/11

!! not ready to be merged yet !!

• adds swing elts for a wavelength range
• reacts to changes in these swing elts by creating a generic filter and setting it in current subset definition
• reacts to changes in collection by modifying swing elts.
  • it always display swing elts for one wavelength range, no matter if the loaded collection had filters or not