Command files: Warn if multiple imports with different args under same name

[Lakitna]

When importing a library, you can provide import arguments.

*** Settings ***
Library    Foo    arg1    arg2

A library should only ever be imported with the same arguments.

Exception: You can rename a library with AS. The following is ok because they are imported under different names:

*** Settings ***
Library    SomeLibrary    localhost        1234    AS    LocalLib
Library    SomeLibrary    server.domain    8080    AS    RemoteLib