Add "Corner" as a valid format type for AMI parameters.

[capn-freako]

Currently, the AMI parser bombs out if Corner has been used as the parameter format for any parameter in the file.

==> Fix this, by adding Corner as a legitimate option for AMI parameter format type.

[capn-freako]

It turns out that lines of this form:

(Corner 1 0 2 )

were already supported, while lines of this form:

(Format Corner 1 0 2 )

were not.

Note: Both mean the same thing, according to the IBIS spec., as the Format is optional.