SinexLoader doesn’t handle multiple historical eccentricities for a same station

When reading the eccentricities file for ILRS stations (https://ilrs.gsfc.nasa.gov/network/site_procedures/eccentricity.html), I realized that Orekit does not support multiple eccentricity entries for a same station. This is used in ILRS stations to indicate the historical detector positions in case it was moved or in case a new survey provides a better estimation of the detector position. For instance for the Yarragadee station (7090), there are 18 entries with each a validity time interval, see ecc_xyz.snx lines 888 to 905.

Looking at the source code in SinexLoader.java from line 232, Orekit's behaviour is the following:

• Set the validity time interval of the Station object based on the first entry found for this station (for Yarragadee, it gives 1979-07-01T00:00:00.000Z to 1983-07-26T23:59:58.000Z)
• Set the eccentricities based on the last entry found for this station (for Yarragadee, it gives [-1.2073; 2.5034; -1.5509])

A possible fix could be:

• Set the validity time interval of the Station object from the start time of the first segment until the end time of the last segment found for this station
• Store all the historical eccentricity data in a TimeSpanMap
• Add a method Station::getEccentricities(AbsoluteDate date) to return the eccentricity value corresponding to the time input by the user
  • To not break existing code, maybe the method Station::getEccentricities() could be kept and could return the latest eccentricity value