Add Alert if Url Param isn't correct

[DanielJDufour]

For example if I write tool=identify instead of tool=IdentifyTool

[DanielJDufour]

Wrote code to check value of tool param, but should also validate all the params too. Perhaps create a validate_url_params function, which lives in a separate file. We should through an alert when accidentally put the wrong param name like url_to_tiff instead of url or hide_menus instead of hide_menu. Alert should also give suggestions on what the correct spelling is.