fix PrimitiveElement vs. PrimitiveRoot

[ThomasBreuer]

In GAP, PrimitiveElement(F) denotes an element that generates F over LeftActingDomain(F), whereas PrimitiveRoot(F) is a generator of the multiplicative group of F if F is a finite field.
In Magma, according to its documentation, PrimitiveElement(F) for a finite field F is always a primitive root.

(Currently the way how finite fields are constructed in GAP seems to guarantee that PrimitiveElement(F) always is a primitive root, like in Magma. Thus there was no problem in practice.)

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 77.87%. Comparing base (016bd68) to head (ca37086).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
lib/magma.gi	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #74      +/-   ##
==========================================
- Coverage   77.89%   77.87%   -0.02%     
==========================================
  Files          29       29              
  Lines        1823     1826       +3     
==========================================
+ Hits         1420     1422       +2     
- Misses        403      404       +1     

Files with missing lines	Coverage Δ
lib/magma.gi	80.11% <75.00%> (-0.23%)	⬇️

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[cdwensley]

Thanks @ThomasBreuer - I was starting to work on this earlier this morning but had no way of checking that PrimitiveElement was still correct the correct term in Magma. I'm intending to move the test for ConvertToMagmaInputString from others.tst to a new magma.tst before releasing a new version.

[cdwensley]

Realised there is no need for a new magma.tst - made some small adjustments to the manual and released v0.88.