ROSS Message Size should be an override configuration

[nmcglo]

Requiring the ROSS message size to be included in the configuration file seems unnecessary to me. Way more often than not, these message sizes are defined at compile time, yet we require a runtime configuration value to specify the size. There's even a check that performs a sizeof() call and compares it with what is configured.

It might be a good idea to make that key:value pair in the configuration file an optional override for when it may be necessary.