Fix issues with SCHISM job scripts customization for different platforms

[SorooshMani-NOAA]

When trying out coupledmodeldriver on ParallelWorks, I realized there are some issues with the existing implementation, and also that it's hard to customize some of the aspects of the run jobs:

• Processors count is not honored
• Number of nodes cannot be specified
• Launcher is "hardcoded" based on Platform enum. Enum objects are not extendable
• The schism job might be more complicated (more commands) than just the executable name after the launcher name
• The combine hotstart job does not need the same resources as the actual run!
• Modules and path prefixes are not customizable (except through including a source file)