Validation of constraints `Length` and `CharCount` might panic about valid

[haraldmaida]

A solution will be to change the type of the limit parameters from u32 to usize. There is one small issue with this solution though. In case of a constraint violations the actual value and the expected value should be converted to Value. This conversion is needed to include the parameters in the ValidationError, or more precisly in the InvalidValue struct.

usize can not be converted to Value for values that are greater than i64::max_value(). To overcome this we can implement TryFrom<usize> for Value and include this parameters only if the convertion is successful.

[haraldmaida]

fixed with commit d3feb44