Misc fixes to translations.

[jonathf]

From #125:
Add a -1 to auxillary variables when in Set.

From #126:
Bugfix for auxillary variables in Set.

From #128:
Reserved name Get_sum bugfix: vectorize:() -> vectorise::()

From #128 and #129:
Exploit equivalence of a (Var) and a(:) (Get, Colon) in MatLab to read the latter as the former.

@taiwuchian, let me know how these fixes works.

[codecov-io]

Codecov Report

Merging #130 into master will decrease coverage by 0.22%.
The diff coverage is 46.15%.

@@ Coverage Diff @@## master #130 +/- ##
==========================================
- Coverage 50.65% 50.43% -0.23% 
==========================================
Files 96 96 Lines 6947 6960 +13 Branches 1788 1792 +4 ==========================================
- Hits 3519 3510 -9 - Misses 2975 3002 +27 + Partials 453 448 -5

Impacted Files	Coverage Δ
src/matlab2cpp/node/frontend.py	94.44% <ø> (ø)	⬆️
src/matlab2cpp/rules/mat.py	3.7% <0%> (-3.06%)	⬇️
src/matlab2cpp/tree/variables.py	35.24% <100%> (+0.5%)	⬆️
src/matlab2cpp/node/backend.py	57.43% <100%> (+0.68%)	⬆️
src/matlab2cpp/rules/_reserved.py	23.01% <100%> (ø)	⬆️
src/matlab2cpp/rules/armadillo.py	57.37% <66.66%> (-6.56%)	⬇️
src/matlab2cpp/rules/cube.py	16.66% <0%> (-5.56%)	⬇️
src/matlab2cpp/configure/armadillo.py	16.88% <0%> (-3.9%)	⬇️
... and 1 more

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