decompose output functional in discretizer

[TiKeil]

fixes #1111

[sdrave]

Only two stylistic things:

• The indentation in the list comprehensions look weird. The for should be aligned with the L/``B` in the line above. (Everything else would be rejected by my linter. At least it should be indented by a multiple of 4.)

• I think I have never seen v_ before. AFAIK a trailing underscore is only used for keywords. I would probably use vv or so.

[TiKeil]

Only two stylistic things:

* The indentation in the list comprehensions look weird. The `for` should be aligned with the `L`/``B` in the line above. (Everything else would be rejected by my linter. At least it should be indented by a multiple of 4.)

* I think I have never seen `v_` before. AFAIK a trailing underscore is only used for keywords. I would probably use `vv` or so.

Sounds good. I have changed the code appropriately

[codecov]

Codecov Report

Merging #1112 into master will decrease coverage by 0.02%.
The diff coverage is 45.45%.

Impacted Files	Coverage Δ
src/pymor/discretizers/builtin/cg.py	89.07% <45.45%> (-0.86%)	⬇️
src/pymor/vectorarrays/list.py	84.00% <0.00%> (-0.39%)	⬇️
src/pymor/vectorarrays/numpy.py	84.72% <0.00%> (+0.23%)	⬆️