Lexing and parsing for implements list for services/endpoints.
Parsing and lexing for interfaces definitions.
Emitting interface definitions.
Small bug from copy-paste: intended separate label for interface.
Allow aliasing interfaces.
Emitting implements string for end of endpoint.  Note that there's a
semi-ugly bug.  If declare an interface in same file as endpoint that
implements it, must add an alias.  Eg.,

alias Interface Something as '';

Interface Something
{
    ...
}

Endpoint OtherThing implements Something
{
    ....
}

instead of without first alias line.
Added tests to ensure that new interface/implements code works correctly.