Support keyword arguments in CallJuliaFunctionWithCatch, and a few other improvements

[ThomasBreuer]

(motivated mainly by gap-packages/PackageManager/pull/134 and the issues mentioned there)

• support keyword arguments in CallJuliaFunctionWithCatch

• do not use the deprecated and undocumented Core._apply

• update the initializations in init_packagemanager: Replacing PKGMAN_DownloadURL is no longer needed, replacing PKGMAN_RemoveDir was in a wrong place.

• start better documentation of Julia syntax features

[codecov]

Codecov Report

Attention: Patch coverage is 95.65217% with 1 line in your changes missing coverage. Please review.

Project coverage is 74.44%. Comparing base (785a93a) to head (4a847f0).
Report is 9 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/JuliaInterface/gap/calls.gi	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1043      +/-   ##
==========================================
+ Coverage   74.39%   74.44%   +0.05%     
==========================================
  Files          55       55              
  Lines        4527     4540      +13     
==========================================
+ Hits         3368     3380      +12     
- Misses       1159     1160       +1     

Files with missing lines	Coverage Δ
pkg/JuliaInterface/gap/JuliaInterface.gd	100.00% <ø> (ø)
src/packages.jl	72.89% <100.00%> (ø)
src/utils.jl	56.41% <100.00%> (+7.92%)	⬆️
pkg/JuliaInterface/gap/calls.gi	96.66% <90.90%> (-3.34%)	⬇️

[fingolfin]

Did you verify that PackageManager still uses Julia's download feature? I am asking because the weird error about "could not import Downloads" suggests to me that perhaps JuliaImportPackage("Downloads") returns false and so the PackageManager code is not being loaded...

[ThomasBreuer]

Yes, this was also my understanding:
Whenever the warning occurs, the overwrite inside PackageManager does not happen, but up to now, we were anyhow overwriting the function afterwards, thus the code in PackageManager was actually never used.

With gap-packages/PackageManager/pull/134, the problem with the warning should disappear. It depends on the version of PackageManager used whether we can safely remove the code from GAP.jl.

[fingolfin]

I am happy with this but I'd suggest we wait until after PR #1029 is in, just to make sure we don't delay that one further.