Improve 'array too long' message by giving the parameter letter

[dc42]

The 'array too long' message would be more helpful if the parameter letter whose value is being parsed was included in the error message. See for example https://forum.duet3d.com/topic/33513/startup-error-on-rrf-3-5-0-rc1.

[dc42]

The exception that gets thrown when this error occurs accepts only one parameter. Currently we pass the maximum length as the parameter. Do we want the message to include the parameter letter instead of the maximum length?

[dc42]

Changed in 3.5-dev so that the error message reports the parameter letter instead of the maximum length when in standalone mode.