Merge branch 'release/1.13' into stable
Bump to 2.0.0-beta
Add breaking changes info.
Remove duplicate Percent unit.
Rename plural of percent.

Using singular name in plural form sounded most natural, both alternatives are valid.

* Regenerate code and tests.
Bump nuget to 2.0.0 RTM.
Merge branch 'release/2.0.0' into stable
Merge tag '2.0.0' into develop

Release 2.0.0
Bump to 2.1.0 alpha for development.
Merge branch 'develop' of https://github.com/InitialForce/UnitsNet into develop