PrismCL: Allow "-switch:options file" as well as "-switch file:options".

[davexparker]

The former is (now) preferred since (a) it allows a consistent way of providing options to switches, even when there is no filename; and (b) switch names, unlike file names, can never contain a :

[merkste]

For consistency, easier remembrance and a simpler parser, we should consider

-switch :options

Note the space which makes it syntactically similar to the already supported

-switch file:options

However, if we aim to overhaul the argument parser in the future (potentially using an established framework), I suggest to postpone this change until then.