doc fixes

[ddavidebor]

• remove units from docs
• fix install tutorial

[ddavidebor]

Fixed. Warning about the relative links in the docs to fix:

WARNING -  The page "index.md" contained a hyperlink to "constants.md" which is not listed in the "pages" configuration.
WARNING -  The page "index.md" contained a hyperlink to "functions/index.md" which is not listed in the "pages" configuration.
WARNING -  The page "operators.md" contained a hyperlink to "../datatypes/numbers.md" which is not listed in the "pages" configuration.
WARNING -  The page "operators.md" contained a hyperlink to "../datatypes/units.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions.md" contained a hyperlink to "functions/index.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions.md" contained a hyperlink to "functions/forEach.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions.md" contained a hyperlink to "functions/map.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions.md" contained a hyperlink to "functions/format.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions.md" contained a hyperlink to "functions/print.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/bignumber.md" contained a hyperlink to "functions/index.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/boolean.md" contained a hyperlink to "functions/index.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/complex.md" contained a hyperlink to "functions/index.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/filter.md" contained a hyperlink to "functions/forEach.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/filter.md" contained a hyperlink to "functions/map.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/matrix.md" contained a hyperlink to "functions/index.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/number.md" contained a hyperlink to "functions/index.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/sort.md" contained a hyperlink to "functions/forEach.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/sort.md" contained a hyperlink to "functions/map.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/sparse.md" contained a hyperlink to "functions/index.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/stirlingS2.md" contained a hyperlink to "functions/Bell numbers.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/string.md" contained a hyperlink to "functions/index.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/subset.md" contained a hyperlink to "functions/index.md" which is not listed in the "pages" configuration.
WARNING -  The page "functions/unit.md" contained a hyperlink to "functions/index.md" which is not listed in the "pages" configuration.