Incorrect variable names in generated cucumber expressions

[aslakhellesoy]

When I define a parameter type with name country-code and have a snippet generated, the variable name is the same as the parameter type name (country-code). This is not valid Java, nor is it conventional casing. It should be countryCode.

We should remove common invalid characters, and add an enum option for camelcase or snakecase. (In Java it will always be camelCase, but the Go library should use the option - when used inside cucumber-engine it will have to support both, depending on the front-end language).

[mpkorstanje]

Because this is part of the snippet generation and because it shares several common parts with snippet generation this has to be solved in in a language specific implementation. Probably not worth extracting it though.

Moving this to JVM.