vectorization/broadcasting fixes
add oberving example
Added multiple path test for GCRS<->AltAz
Fixes in iers suggested by @mhvk
AstropyDeprecationWarning -> AstropyWarning
Doc updates
Add priorities to disambiguate the <-ICRS<->CIRS<->ITRS<->GCRS-> loop
Fixed unit on testing utility function
Typo fixes suggested by @cdeil

[ci skip]