robot: make interacting with file dialogs easier

[haysmark]

The async parameter on keyPress makes it possible to interact with modal browser dialogs, in particular file upload dialogs. However, when you need to type full path names, it is tedious to type the whole string with async keyPresses.

One way to make this easier on people would be to introduce an async parameter on typeKeys. However, this is not a trivial change; it would require a separate logic branch in typeKeys because the current setTimeout implementation would not execute in all browsers while the dialog is up.

Also, different OSes require using different file delimiters, like / vs
in your string. Java sets a property that tells you what the system file delimiter is; it's only a matter of exposing this delimiter to the doh.robot API.

[bill]

Given the age of this ticket I assume it won't be fixed; we'll likely switch to using WebDriver? and it won't be an issue anymore.