Fix compilation tests

Explicitly casting ratio to target type on unit cast

Update changelog

Add function as() to cast conveniently between units of the same type

Update changelog

Add string operations to acceleration types

Merge pull request #96 from bernedom/feature/add_degree_t

Feature/add degree t

Merge pull request #95 from bernedom/bugfix/fix-missing-conversion-fo…

…r-division

Bugfix/fix missing conversion for division

Merge pull request #92 from bernedom/building/update-to-catch-2.13.6

Building/update to catch 2.13.6

Merge pull request #91 from bernedom/building/try-for-systeminstalled…

…-catch

Building/try for systeminstalled catch