Remove unnecessary format strings

[tmilnthorp]

Remove:

• "V" and "v"
• "S" and "s".

Instead of "v", use IQuantity.Value.ToString() to get the value string.
Instead of "s", use "f2", "n4" or any of the standard numeric formats.

See https://github.com/angularsen/UnitsNet/wiki/String-Formatting

[angularsen]

Fixed in v5 branch.