Enable service names with non-alphanum characters

[daogrady]

Allows "proper" naming of service containing non-alphanumeric names:

service "Foo/Bar" {}

would become

class __Foo_Bar {}  // not exported directly
export { __Foo_Bar as "Foo/Bar" }

and users would have to import like so:

import { "Foo_Bar" as FooBar } from ...
//                      ^ any alias

Note that this creates a discrepancy between service that don't contain special characters, as they are exported as default export, and ones that have names containing special characters, that are only exported in named style.

• [ ] add tests
• [ ] output warning when such a service name is used, as this requires the use of [email protected] or higher.