Classes and app to compute satellite visibility

Changes for 0.130_02 - 2024-03-03

• Cemtralize POSIX::strftime calls to ::Utils::my_strftime
• Refurbish some of the eg/* scripts which have not kept track with API changes of various sorts.
• Correct bug in ::TLE->__make_tle_epoch(). The fractional part was wrong for negative epochs.