Can't have multiple same original

[tbayart]

I found your extension in Chrome web store and it's usefull. I found an issue when I came back to options after I added an original url twice. The first inserted redirect have disapeared, even it was disabled. For me it's useful to have one redirect source and multiple targets to test multiple environments. Correct behavior should be allowing multiple entries with same origin but automatically disabling other same origins, allowing 0 or 1 origin enabled.