Check for updates in externals/spdfcdas and externals/spdfssc

[jameswilburlewis]

I just fixed a bug in spdfssc/spdfreset__define.pro that was causing a crash when trying to load GOES orbit data using a proxy.

It's been quite a while since we pulled any updates of these libraries from SPDF. We should probably check to see if there are other features or bug fixes that we're missing. And if that specific bug is still present, we should send them our patch.

[jameswilburlewis]

Latest software versions from SPDF are:

spdfcdas: 1.8.20
spdfssc: 2.4

Our copies in SPEDAS have some modifications that will need to be repeated when integrating the updated files:

• spdfcdas depends on CDAWlib, but we only include a limited subset (all routines renamed with prefix spd_cdawlib_). So calls will need to be renamed
• We have some calls to explicitly resolve routines from the SPEDAS cdawlib subset
• spdfcdas and spdfssc had some files in common which we resolved by using the ones from spdfcdas and deleting the copies from spdfssc
• Check that spdfcdas doesn't pull in any new dependencies from cdawlib outside of our subset