Rename documentation files.

cli/answertests_docs.php

doc/docslib.php

doc/en/AbInitio/Authoring_quick_start_3.md

doc/en/AbInitio/Authoring_quick_start_8.md

doc/en/About/The_philosophy_of_STACK.md

doc/en/About/index.md

doc/en/Authoring/Answer_Tests/Calculus.md

doc/en/Authoring/Answer_Tests/Equivalence.md

doc/en/Authoring/Answer_Tests/Form.md

doc/en/Authoring/Answer_Tests/Numerical.md

doc/en/Authoring/Answer_Tests/Other.md

doc/en/Authoring/Answer_Tests/Results/AlgEquiv.md

doc/en/Authoring/Answer_Tests/Results/AlgEquivNouns.md

doc/en/Authoring/Answer_Tests/Results/CasEqual.md

doc/en/Authoring/Answer_Tests/Results/CompSquare.md

doc/en/Authoring/Answer_Tests/Results/Diff.md

doc/en/Authoring/Answer_Tests/Results/EqualComAss.md

doc/en/Authoring/Answer_Tests/Results/EqualComAssRules.md

doc/en/Authoring/Answer_Tests/Results/Equiv.md

doc/en/Authoring/Answer_Tests/Results/EquivFirst.md